Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2017	Feb. 23, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	KIRBY CORP
Entity Central Index Key	0000056047
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 3,511,931,000
Entity Common Stock, Shares Outstanding		59,674,000
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 20,102	$ 5,634
Accounts receivable:
Trade - less allowance for doubtful accounts of $8,930 ($7,240 in 2016)	452,222	297,177
Other	106,231	95,327
Inventories - at lower of average cost or market	315,729	185,402
Prepaid expenses and other current assets	62,798	49,411
Total current assets	957,082	632,951
Property and equipment:
Marine transportation equipment	3,941,379	4,071,972
Land, buildings and equipment	419,503	256,925
Property and equipment	4,360,882	4,328,897
Accumulated depreciation	1,401,617	1,407,523
Property and equipment - net	2,959,265	2,921,374
Investment in affiliates	1,890	2,622
Goodwill	935,135	598,131
Other intangibles, net	232,808	87,306
Other assets	41,247	47,511
Total assets	5,127,427	4,289,895
Current liabilities:
Bank notes payable	3	0
Income taxes payable	191	3,288
Accounts payable	222,005	134,571
Accrued liabilities:
Interest	6,099	5,397
Insurance premiums and claims	108,651	123,371
Employee compensation	45,193	26,916
Taxes - other than on income	22,791	15,481
Other	27,026	13,313
Deferred revenues	48,347	36,001
Total current liabilities	480,306	358,338
Long-term debt - less current portion	992,403	722,802
Deferred income taxes	468,451	705,453
Other long-term liabilities	72,044	90,435
Total long-term liabilities	1,532,898	1,518,690
Contingencies and commitments
Kirby stockholders' equity:
Common stock, $.10 par value per share. Authorized 120,000,000 shares, issued 65,472,000 in 2017 and 59,776,000 in 2016	6,547	5,978
Additional paid-in capital	802,961	432,459
Accumulated other comprehensive income - net	(32,405)	(51,007)
Retained earnings	2,646,937	2,342,236
Treasury stock - at cost, 5,783,000 shares in 2017 and 5,921,000 in 2016	(313,220)	(320,348)
Total Kirby stockholders' equity	3,110,820	2,409,318
Noncontrolling interests	3,403	3,549
Total equity	3,114,223	2,412,867
Total liabilities and equity	$ 5,127,427	$ 4,289,895

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Trade, allowance for doubtful accounts	$ 8,930	$ 7,240
Kirby stockholders' equity:
Common stock, par value per share (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized (in shares)	120,000,000	120,000,000
Common stock, shares issued (in shares)	65,472,000	59,776,000
Treasury stock, shares (in shares)	5,783,000	5,921,000

CONSOLIDATED STATEMENTS OF EARNINGS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Marine transportation	$ 1,324,106	$ 1,471,893	$ 1,663,090
Distribution and services	890,312	298,780	484,442
Total revenues	2,214,418	1,770,673	2,147,532
Costs and expenses:
Costs of sales and operating expenses	1,557,564	1,126,952	1,362,366
Selling, general and administrative	220,364	174,752	193,237
Taxes, other than on income	29,163	22,730	20,699
Depreciation and amortization	202,881	200,917	192,240
Impairment of long-lived assets	105,712	0	0
Loss (gain) on disposition of assets	4,487	127	(1,672)
Total costs and expenses	2,120,171	1,525,478	1,766,870
Operating income	94,247	245,195	380,662
Equity in earnings of affiliates	291	532	451
Other expense	(52)	(291)	(663)
Interest expense	(21,472)	(17,690)	(18,738)
Earnings before taxes on income	73,014	227,746	361,712
Benefit (provision) for taxes on income	240,889	(84,942)	(133,742)
Net earnings	313,903	142,804	227,970
Less: Net earnings attributable to noncontrolling interests	(716)	(1,398)	(1,286)
Net earnings attributable to Kirby	$ 313,187	$ 141,406	$ 226,684
Net earnings per share attributable to Kirby common stockholders:
Basic (in dollars per share)	$ 5.62	$ 2.63	$ 4.12
Diluted (in dollars per share)	$ 5.62	$ 2.62	$ 4.11

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net earnings	$ 313,903	$ 142,804	$ 227,970
Other comprehensive income (loss), net of taxes:
Pension and postretirement benefits	18,748	(6,321)	16,322
Foreign currency translation adjustments	(146)	0	29
Total other comprehensive income (loss), net of taxes	18,602	(6,321)	16,351
Total comprehensive income, net of taxes	332,505	136,483	244,321
Net earnings attributable to noncontrolling interests	(716)	(1,398)	(1,286)
Comprehensive income attributable to Kirby	$ 331,789	$ 135,085	$ 243,035

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net earnings	$ 313,903	$ 142,804	$ 227,970
Adjustments to reconcile net earnings to net cash provided by operations:
Depreciation and amortization	202,881	200,917	192,240
Provision (credit) for doubtful accounts	224	(467)	1,426
Provision (benefit) for deferred income taxes	(256,263)	51,296	62,755
Loss (gain) on disposition of assets	4,487	127	(1,672)
Equity in earnings of affiliates, net of distributions and contributions	732	(532)	449
Impairment of long-lived assets	105,712	0	0
Amortization of unearned share-based compensation	11,460	11,675	11,104
Amortization of major maintenance costs	21,207	19,869	22,126
Amortization of debt issuance costs	986	801	1,377
Increase (decrease) in cash flows resulting from changes in:
Accounts receivable	(60,405)	(12,750)	129,908
Inventory	19,673	3,182	(7,320)
Other assets	(17,049)	(30,853)	(15,551)
Income taxes payable	(11,823)	15,413	477
Accounts payable	20,758	(1,739)	(81,808)
Accrued and other liabilities	(3,105)	16,051	(19,201)
Net cash provided by operating activities	353,378	415,794	524,280
Cash flows from investing activities:
Capital expenditures	(177,222)	(231,066)	(345,475)
Acquisitions of businesses and marine equipment, net of cash acquired	(470,101)	(137,072)	(41,250)
Proceeds from disposition of assets	54,229	18,617	24,429
Net cash used in investing activities	(593,094)	(349,521)	(362,296)
Cash flows from financing activities:
Borrowings (payments) on bank credit facilities, net	268,616	(52,848)	160,784
Payments on long-term debt	(13,721)	0	(100,000)
Return of investment to noncontrolling interests	(862)	(1,976)	(1,778)
Proceeds from exercise of stock options	3,039	321	3,712
Purchase of treasury stock	0	(1,827)	(241,105)
Payments related to tax withholding for share-based compensation	(2,881)	(1,756)	(2,975)
Acquisitions of noncontrolling interest	(7)	(8,438)	0
Excess tax benefit from equity compensation plans	0	0	964
Net cash provided by (used in) financing activities	254,184	(66,524)	(180,398)
Increase (decrease) in cash and cash equivalents	14,468	(251)	(18,414)
Cash and cash equivalents, beginning of year	5,634	5,885	24,299
Cash and cash equivalents, end of year	20,102	5,634	5,885
Cash paid during the period:
Interest paid	21,663	19,878	20,586
Income taxes paid	27,196	18,162	69,584
Capital expenditures included in accounts payable	5,525	(2,037)	2,206
Non-cash investing activity:
Fair value of property transferred in acquisition	0	3,681	0
Stock issued in acquisition	366,554	0	0
Cash acquired in acquisition	98	0	0
Debt assumed in acquisition	$ 13,724	$ 0	$ 0

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Noncontrolling Interests [Member]	Total
Cumulative effect of adoption of ASU 2016-09				$ 0
Balance at beginning of year at Dec. 31, 2014	$ 5,978	$ 428,475	$ (61,037)	1,974,146	$ (93,526)	$ 10,877
Issuance of shares in acquisition	0	0
Excess (deficit) of proceeds received upon exercise of stock options and issuance of restricted stock over cost of treasury stock issued		3,530
Tax benefit (expense) realized from equity compensation plans		964
Issuance of restricted stock, net of forfeitures		(9,290)
Amortization of unearned compensation		11,104
Acquisitions of noncontrolling interests		0				0
Net earnings attributable to Kirby for the year				226,684			$ 226,684
Purchase of treasury stock (35,000 in 2016 and 3,316,000 in 2015)					(241,105)
Cost of treasury stock issued upon exercise of stock options and issuance of restricted stock (138,000 in 2017, 170,000 in 2016 and 166,000 in 2015)					6,537
Net earnings attributable to noncontrolling interests						1,286	1,286
Return of investment to noncontrolling interests						(1,778)	1,778
Other comprehensive income (loss), net of taxes			16,351				16,351
Balance at end of year at Dec. 31, 2015	5,978	434,783	(44,686)	2,200,830	(328,094)	10,385
Cumulative effect of adoption of ASU 2016-09				0
Issuance of shares in acquisition	0	0
Excess (deficit) of proceeds received upon exercise of stock options and issuance of restricted stock over cost of treasury stock issued		(755)
Tax benefit (expense) realized from equity compensation plans		(824)
Issuance of restricted stock, net of forfeitures		(10,218)
Amortization of unearned compensation		11,675
Acquisitions of noncontrolling interests		(2,202)				(6,258)
Net earnings attributable to Kirby for the year				141,406			141,406
Purchase of treasury stock (35,000 in 2016 and 3,316,000 in 2015)					(1,827)
Cost of treasury stock issued upon exercise of stock options and issuance of restricted stock (138,000 in 2017, 170,000 in 2016 and 166,000 in 2015)					9,573
Net earnings attributable to noncontrolling interests						1,398	1,398
Return of investment to noncontrolling interests						(1,976)	1,976
Other comprehensive income (loss), net of taxes			(6,321)				(6,321)
Balance at end of year at Dec. 31, 2016	5,978	432,459	(51,007)	2,342,236	(320,348)	3,549	2,412,867
Cumulative effect of adoption of ASU 2016-09 \| ASU 2016-09 [Member]				(8,486)			8,486
Issuance of shares in acquisition	569	365,985
Excess (deficit) of proceeds received upon exercise of stock options and issuance of restricted stock over cost of treasury stock issued		833
Tax benefit (expense) realized from equity compensation plans		0
Issuance of restricted stock, net of forfeitures		(7,770)
Amortization of unearned compensation		11,460
Acquisitions of noncontrolling interests		(6)				0
Net earnings attributable to Kirby for the year				313,187			313,187
Purchase of treasury stock (35,000 in 2016 and 3,316,000 in 2015)					0
Cost of treasury stock issued upon exercise of stock options and issuance of restricted stock (138,000 in 2017, 170,000 in 2016 and 166,000 in 2015)					7,128
Net earnings attributable to noncontrolling interests						716	716
Return of investment to noncontrolling interests						(862)	862
Other comprehensive income (loss), net of taxes			18,602				18,602
Balance at end of year at Dec. 31, 2017	$ 6,547	$ 802,961	$ (32,405)	$ 2,646,937	$ (313,220)	$ 3,403	$ 3,114,223

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - Treasury Stock [Member] - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Purchase of treasury stock (in shares)	0	35,000	3,316,000
Treasury stock issued upon exercise of stock options and issuance of restricted stock (in shares)	138,000	170,000	166,000

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	(1) Summary of Significant Accounting Policies Principles of Consolidation. The consolidated financial statements include the accounts of Kirby Corporation and all majority-owned subsidiaries (“the Company”). All investments in which the Company owns 20% to 50% and exercises significant influence over operating and financial policies are accounted for using the equity method. All material intercompany accounts and transactions have been eliminated in consolidation. Certain reclassifications have been made to reflect the current presentation of financial information. Accounting Policies Cash Equivalents. Cash equivalents consist of all short-term, highly liquid investments with maturities of three months or less at date of purchase. Accounts Receivable. In the normal course of business, the Company extends credit to its customers. The Company regularly reviews the accounts and makes adequate provisions for probable uncollectible balances. It is the Company’s opinion that the accounts have no impairment, other than that for which provisions have been made. Included in accounts receivable as of December 31, 2017 and 2016 were $153,661,000 and $84,453,000, respectively, of accruals for revenues earned which have not been invoiced as of the end of each year. The Company’s marine transportation and distribution and services operations are subject to hazards associated with such businesses. The Company maintains insurance coverage against these hazards with insurance companies. Included in accounts receivable as of December 31, 2017 and 2016 were $66,588,000 and $88,182,000, respectively, of receivables from insurance companies to cover claims in excess of the Company’s deductible. Concentrations of Credit Risk. Financial instruments which potentially subject the Company to concentrations of credit risk are primarily trade accounts receivables. The Company’s marine transportation customers include the major oil refining and petrochemical companies. The distribution and services customers are oilfield service companies, oil and gas operators and producers, on-highway transportation companies, marine transportation companies, commercial fishing companies, construction companies, mining companies, power generation companies, and the United States government. The Company regularly reviews its accounts and estimates the amount of uncollectible receivables each period and establishes an allowance for uncollectible amounts. The amount of the allowance is based on the age of unpaid amounts, information about the current financial strength of customers, and other relevant information. Estimates of uncollectible amounts are revised each period, and changes are recorded in the period they become known. Fair Value of Financial Instruments. Cash, accounts receivable, accounts payable and accrued liabilities have carrying values that approximate fair value due to the short-term maturity of these financial instruments. The fair value of the Company’s debt instruments is more fully described in Note 6, Long-Term Debt. Property, Maintenance and Repairs. Property is recorded at cost. Improvements and betterments are capitalized as incurred. Depreciation is recorded on the straight-line method over the estimated useful lives of the individual assets as follows: marine transportation equipment, 5-40 years; buildings, 10-40 years; other equipment, 2-10 years; and leasehold improvements, term of lease. When property items are retired, sold or otherwise disposed of, the related cost and accumulated depreciation are removed from the accounts with any gain or loss on the disposition included in the statement of earnings. Maintenance and repairs on vessels built for use on the inland waterways are charged to operating expense as incurred and includes the costs incurred in United States Coast Guard (“USCG”) inspections unless the shipyard extends the life or improves the operating capacity of the vessel which results in the costs being capitalized. Drydocking on Ocean-Going Vessels. The Company’s ocean-going vessels are subject to regulatory drydocking requirements after certain periods of time to be inspected, have planned major maintenance performed and be recertified by the American Bureau of Shipping (“ABS”). These recertifications generally occur twice in a five year period. The Company defers the drydocking expenditures incurred on its ocean-going vessels due to regulatory marine inspections by the ABS and amortizes the costs of the shipyard over the period between drydockings, generally 30 or 60 months, depending on the type of major maintenance performed. Drydocking expenditures that extend the life or improve the operating capability of the vessel result in the costs being capitalized. The Company recognized amortization of major maintenance costs of $21,207,000, $19,869,000 and $22,126,000 for the years ended December 31, 2017, 2016 and 2015, respectively, in costs of sales and operating expenses. Routine repairs and maintenance on ocean-going vessels are expensed as incurred. Interest is capitalized on the construction of new ocean-going vessels. Interest expense excludes capitalized interest of $1,731,000, $2,974,000 and $3,026,000 for the years ending December 31, 2017, 2016 and 2015, respectively. Environmental Liabilities. The Company expenses costs related to environmental events as they are incurred or when a loss is considered probable and estimable. Goodwill. The excess of the purchase price over the fair value of identifiable net assets acquired in transactions accounted for as a purchase is included in goodwill. The Company conducted its annual goodwill impairment test at November 30, 2017 and 2016. For 2017 and 2016, the Company noted no impairment of goodwill. The Company will continue to conduct goodwill impairment tests as of November 30 of subsequent years, or whenever events or circumstances indicate that interim impairment testing is necessary. The amount of goodwill impairment, if any, is typically measured based on projected discounted future operating cash flows using an appropriate discount rate. The gross carrying value of goodwill at December 31, 2017 and 2016 was $947,502,000 and $615,598,000, respectively, and accumulated amortization at December 31, 2017 and 2016 was $15,566,000. Accumulated impairment losses were $1,901,000 at December 31, 2017 and 2016. Net goodwill for the marine transportation segment was $387,504,000 and $382,227,000 at December 31, 2017 and 2016, respectively. The increase in net goodwill for the marine transportation segment for 2017 was due to the purchase of a barge fleeting and marine fueling operation, as well as San Jac Marine, LLC (“San Jac”), which are more fully described in Note 2, Acquisitions. Net goodwill for the distribution and services segment was $547,631,000 and $215,904,000 at December 31, 2017 and 2016, respectively. The increase in net goodwill for the distribution and services segment was due to the acquisition of Stewart & Stevenson LLC (“S&S”) in 2017, also more fully described in Note 2, Acquisitions. Other Intangibles. Other intangibles include assets for customer contracts and relationships, distributorship and dealership agreements, trade names and noncompete agreements and liabilities for unfavorable leases. As of December 31, 2017 and 2016, the gross carrying amounts of other intangible assets were $315,983,000 and $158,634,000, respectively, and the accumulated amortization was $83,175,000 and $71,328,000, respectively, resulting in net carrying amounts of $232,808,000 and $87,306,000, respectively. As of December 31, 2017 and 2016, the gross carrying amounts of other intangible liabilities were $7,437,000 and $5,759,000, respectively, and the accumulated amortization was $4,751,000 and $3,949,000, respectively, resulting in net carrying amounts of $2,686,000 and $1,810,000, respectively. The costs of intangible assets and liabilities are amortized to expense in a systematic and rational manner over their estimated useful lives. For the years ended December 31, 2017, 2016 and 2015, the amortization expense for intangibles was $11,296,000, $8,467,000 and $8,526,000, respectively. Estimated amortization expense for amortizable intangible assets and liabilities for the next five years (2018 – 2022) is approximately $17,760,000, $17,395,000, $17,617,000, $17,171,000 and $16,971,000, respectively. As of December 31, 2017, the weighted average amortization period for intangible assets and liabilities was approximately 15 years. Revenue Recognition. The majority of marine transportation revenue is derived from term contracts, ranging from one to five years, some of which have renewal options, and the remainder is from spot market movements. The majority of the term contracts are for terms of one year. The Company is a provider of marine transportation services for its customers and, in almost all cases, does not assume ownership of the products it transports. A term contract is an agreement with a specific customer to transport cargo from a designated origin to a designated destination at a set rate or at a daily rate. The rate may or may not escalate during the term of the contract, however, the base rate generally remains constant and contracts often include escalation provisions to recover changes in specific costs such as fuel. A spot contract is an agreement with a customer to move cargo from a specific origin to a designated destination for a rate negotiated at the time the cargo movement takes place. Spot contract rates are at the current “market” rate, including fuel, and are subject to market volatility. The Company uses a voyage accounting method of revenue recognition for its marine transportation revenues which allocates voyage revenue based on the percent of the voyage completed during the period. There is no difference in the recognition of revenue between a term contract and a spot contract. Distribution products and services are generally sold based upon purchase orders or preferential service agreements with the customer that include fixed or determinable prices and that do not include right of return or significant post-delivery performance obligations. Parts sales are recognized when title passes upon shipment to customers or when customer-specific acceptance requirements are met. Service revenue is recognized as the service is provided. Revenue from rental agreements is recognized on a straight-line basis over the rental period. Distribution and services manufacturing and assembly projects revenue is reported on the percentage of completion method of accounting using measurements of progress towards completion appropriate for the work performed. Stock-Based Compensation. The Company has share-based compensation plans covering selected officers and other key employees as well as the Company’s Board of Directors. Stock-based grants made under the Company’s stock plans are recorded at fair value on the date of the grant and the cost is recognized ratably over the vesting period of the stock option or restricted stock. Stock option grants are valued at the date of grant as calculated under the Black-Scholes option pricing model. The Company’s stock-based compensation plans are more fully described in Note 9, Stock Award Plans. Taxes on Income. The Company follows the asset and liability method of accounting for income taxes. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Accrued Insurance. Accrued insurance liabilities include estimates based on individual incurred claims outstanding and an estimated amount for losses incurred but not reported (“IBNR”) or fully developed based on past experience. Insurance premiums, IBNR losses and incurred claim losses, in excess of the Company’s deductible for 2017, 2016 and 2015 were $26,195,000, $23,085,000 and $23,737,000, respectively. Noncontrolling Interests. The Company has a majority interest in and is the general partner in several affiliated entities. In situations where losses applicable to the minority interest in the affiliated entities exceed the limited partners’ equity capital, such excess and any further loss attributable to the minority interest is charged against the Company’s interest in the affiliated entities. If future earnings materialize in the respective affiliated entities, the Company’s interest would be credited to the extent of any losses previously absorbed. Treasury Stock. The Company follows the average cost method of accounting for treasury stock transactions. Impairment of Long-lived Assets and for Long-lived Assets to Be Disposed Of. The Company reviews long-lived assets and certain identifiable intangibles for impairment by vessel class whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. Recoverability on marine transportation assets is assessed based on vessel classes, not on individual assets, because identifiable cash flows for individual marine transportation assets are not available. Projecting customer contract volumes allows estimation of future cash flows by projecting pricing and utilization by vessel class but it is not practical to project which individual marine transportation asset will be utilized for any given contract. Because customers do not specify which particular vessel is used, prices are quoted based on vessel classes not individual assets. Nominations of vessels for specific jobs are determined on a day by day basis and are a function of the equipment class required and the geographic position of vessels within that class at that particular time as vessels within a class are interchangeable and provide the same service. The Company’s vessels are mobile assets and equipped to operate in geographic regions throughout the United States and the Company has in the past and expects to continue to move vessels from one region to another when it is necessary due to changing markets and it is economical to do so. Barge vessel classes are based on similar capacities, hull type, and type of product and towing vessels are based on similar hull type and horsepower. Recoverability of the vessel classes is measured by a comparison of the carrying amount of the assets to future net cash flows expected to be generated by the assets. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. Accounting Standards In February 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-02, “Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the recent federal tax reform legislation. ASU 2018-02 eliminates the stranded tax effects resulting from the recent federal tax reform legislation and will improve the usefulness of information reported to financial statement users. The amendments in ASU 2018-02 will be applied either in the period of adoption or retrospectively to each period (or periods) in which the effect of the change in the recent federal tax reform legislation is recognized. ASU 2018-02 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted, including adoption in any interim period, for which financial statements have not yet been made available for issuance. The Company is currently evaluating the impact, if any, that the adoption of this standard will have on its consolidated financial statements. In March 2017, the FASB issued ASU 2017-07, “Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost” (“ASU 2017-07”) which requires employers to include only the service cost component of net periodic pension cost and net periodic postretirement benefit cost in operating expenses. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations. The standard allows only the service cost component to be eligible for capitalization when applicable. ASU 2017-07 is effective for annual and interim periods beginning after December 15, 2017 with early adoption permitted. This standard shall be applied retrospectively for the presentation of the service cost component and the other components of net periodic pension cost and net periodic postretirement benefit cost in the income statement and prospectively for the capitalization of the service cost benefit in assets. The Company will adopt the provisions of ASU 2017-07 on January 1, 2018 and the Company does not expect the adoption of ASU 2017-07 to have a material impact on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, “Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment” (“ASU 2017-04”) which simplifies the subsequent measurement of goodwill by eliminating Step 2 in the goodwill impairment test that required an entity to perform procedures to determine the fair value of its assets and liabilities at the testing date. An entity instead will perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying value and record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. ASU 2017-04 will be applied prospectively and is effective for annual and interim goodwill impairment tests conducted in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment testing dates after January 1, 2017. The Company is currently evaluating the impact, if any, that the adoption of this standard will have on its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments” (“ASU 2016-15”) to create consistency in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. ASU 2016-15 is effective for annual and interim periods beginning after December 15, 2017. The Company will adopt the provisions of ASU 2016-15 on January 1, 2018 and the Company does not expect the adoption of ASU 2016-15 to have a material impact on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, “Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”) which simplifies several aspects of the accounting for share-based payment transactions, including income tax consequences, forfeitures, minimum statutory tax withholding requirements, classification as either equity or liabilities, and classification on the statement of cash flows. The Company adopted the provisions of ASU 2016-09 on January 1, 2017. ASU 2016-09 requires all excess tax benefits and tax deficiencies be recognized as income tax expense or benefit in the income statement, thus eliminating additional paid-in capital pools. The Company recognized a cumulative effect adjustment of $8,486,000 to retained earnings on a modified retrospective basis as of January 1, 2017 and will apply the new standard guidance prospectively to all excess tax benefits and tax deficiencies resulting from settlements after January 1, 2017. The standard also requires a policy election to either estimate the number of awards that are expected to vest or account for forfeitures when they occur. The Company will elect to account for forfeitures when they occur. Also, the standard requires that excess tax benefits should be classified along with other income tax cash flows as an operating activity on the statement of cash flows, which differs from the Company’s historical classification of excess tax benefits as cash inflows from financing activities. The Company elected to apply this provision using the prospective transition method. Additionally, the standard requires cash paid by an employer when directly withholding shares for tax withholding purposes to be classified in the statement of cash flows as a financing activity, which differs from the Company’s previous method of classification of such cash payments as an operating activity. The Company applied this provision retrospectively and reclassified $1,756,000 and $2,975,000 during 2016 and 2015, respectively, which increased net cash provided by operating activities and net cash used in financing activities. In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842)” (“ASU 2016-02”) to increase transparency and comparability among organizations by requiring recognition of lease assets and lease liabilities on the balance sheet and disclosure of key information about leasing arrangements. ASU 2016-02 is effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted. A modified retrospective approach is required. The Company has formed a project team to evaluate the impact that the adoption of this standard will have on its consolidated financial statements and disclosures. The project team has completed training on the new standard and has started lease review and documentation, but the Company has not yet determined the effect of ASU 2016-02 on its ongoing financial reporting. In November 2015, the FASB issued ASU 2015-17, “Balance Sheet Classification of Deferred Taxes” (“ASU 2015-17”) which requires that deferred tax liabilities and assets be classified as noncurrent on the balance sheet. The current requirement that deferred tax liabilities and assets of a tax-paying component of an entity be offset and presented as a single amount is not affected by this guidance. The guidance may be applied either prospectively to all deferred tax liabilities and assets or retrospectively to all periods presented. The Company adopted the provisions of ASU 2015-17 on January 1, 2017 on a retrospective basis. The December 31, 2016 current deferred tax assets of $13,604,000 have been reclassified in the consolidated balance sheet from current deferred income taxes asset to noncurrent deferred income taxes liability. In July 2015, the FASB issued ASU 2015-11, “Inventory (Topic 330): Simplifying the Measurement of Inventory” (“ASU 2015-11”) which applies to inventory that is measured using first-in, first-out (“FIFO”) or average cost. Under the guidance, an entity should measure inventory that is within the scope of this update at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal and transportation. ASU 2015-11 is effective for annual and interim periods beginning after December 15, 2016, and should be applied prospectively with early adoption permitted at the beginning of an interim period or annual reporting period. The Company adopted the provisions of ASU 2015-11 on January 1, 2017 and, based on a lower of cost and net realizable value inventory analysis as of December 31, 2016, no adjustments to inventory value were required. The analysis reflected the inventory values are proper within the guidance of ASU 2015-11. In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers” (“ASU 2014-09”). ASU 2014-09 requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 will replace most existing revenue recognition guidance in United States Generally Accepted Accounting Principles when it becomes effective. In July 2015, the FASB voted to delay the effective date of ASU 2014-09 by one year, making it effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, with early adoption permitted as of the original effective date. ASU 2014-09 permits the use of either the retrospective, modified retrospective or prospective with a cumulative catch-up approach. The Company will adopt ASU 2014-09 on January 1, 2018 with a cumulative adjustment that will decrease retained earnings by approximately $10,000,000 rather than restating previously reported results. The cumulative adjustment will primarily relate to recognition of revenue on certain contract manufacturing activities, primarily construction of new pressure pumping units in the Company’s distribution and services segment. The Company currently recognizes revenue on manufacturing and assembly projects on a percentage of completion method using measurements of progress towards completion appropriate for the work performed. Upon the adoption of ASU 2014-09, the Company will recognize the revenues on contract manufacturing activities upon shipment and transfer of control versus the percentage of completion method.

Acquisitions

12 Months Ended

Dec. 31, 2017

Acquisitions [Abstract]

Acquisitions

(2) Acquisitions

On October 20, 2017, San Jac, a subsidiary of the Company, purchased certain assets of Sneed Shipbuilding, Inc. for $14,852,000 in cash including its Channelview, Texas shipyard. San Jac is a builder of marine vessels for both inland and offshore applications as well providing repair and maintenance services. The Company intends to build towboats at the shipyard and use the facilities for routine maintenance.

On September 13, 2017, the Company completed the acquisition of substantially all of the assets of S&S, a global manufacturer and distributor of products and services for the oil and gas, marine, construction, power generation, transportation, mining and agricultural industries. The acquired business, which the Company operates through a newly formed subsidiary renamed Stewart & Stevenson LLC after the closing of the acquisition, was founded in 1902 and serves domestic and global markets with equipment, rental solutions, parts and service through a strategic network of sales and service centers in domestic and international locations.

The total value of the transaction was $758,245,000, before post-closing adjustments and excluding transaction fees, consisting of cash consideration of $377,967,000, the assumption of $13,724,000 of debt and $366,554,000 through the issuance of 5,696,259 shares of Company common stock valued at $64.35 per share, the Company’s closing share price on September 13, 2017. On June 26, 2017, in advance of the purchase of S&S, the Company entered into an amendment of its revolving credit facility that increased the borrowing limit from $550,000,000 to $850,000,000 and extended the maturity date to June 26, 2022. The debt assumed consisted of $12,135,000 of term debt and $1,589,000 of short-term secured loans related to the Company’s South American operations. The term debt was paid off without penalty in the 2017 fourth quarter.

S&S, headquartered in Houston, Texas with 42 branches across 12 states, is a distributor in certain geographic areas for Allison Transmission, MTU Detroit Diesel, EMD Power Products ("EMD"), Deutz and several other manufacturers. S&S’ principal customers are oilfield service companies, oil and gas operators and producers, and companies in the marine, mining, power generation, on-highway and other commercial and industrial applications.

The Company considers S&S to be a natural extension of the current distribution and services segment, expanding its geographic footprint and capabilities of the distribution and services business.

Total consideration transferred was as follows (in thousands):

Cash consideration paid	$	377,967
Stock consideration through issuance of Company common stock		366,554
Fair value of consideration transferred	$	744,521

The fair values of the assets acquired and liabilities assumed recorded at the acquisition date were as follows (in thousands):

Assets:
Cash	$	98
Accounts receivable		97,891
Inventories		150,000
Prepaid expenses and other current assets		3,850
Property and equipment		141,885
Goodwill		331,728
Other assets		158,130
Total assets	$	883,582


Liabilities:
Current portion of long-term debt	$	1,501
Bank notes payable		1,589
Income taxes payable		850
Accounts payable		72,200
Accrued liabilities		31,803
Deferred revenues		18,806
Long-term debt		10,634
Other long-term liabilities		1,678
Total liabilities	$	139,061
Net assets acquired	$	744,521

The analysis of the S&S fair values is substantially complete but all fair values have not been finalized pending obtaining the information necessary to complete the analysis. As additional information becomes known concerning the assets acquired and liabilities assumed, the Company may make adjustments to the opening balance sheet of S&S up to a one year period following the acquisition date.

As a result of the acquisition, the Company recorded $331,728,000 of goodwill and $155,722,000 of net intangibles. The net intangibles have a weighted average amortization period of approximately 16.8 years. The Company expects substantially all of the goodwill will be deductible for tax purposes. Acquisition related costs of $2,119,000, consisting primarily of legal, audit and other professional fees plus other expenses, were expensed as incurred to selling general and administrative expense in 2017.

On July 10, 2017, the Company completed the purchase of certain inland marine assets from an undisclosed competitor for $68,000,000 in cash. The assets purchased consisted of nine specialty pressure tank barges, four 30,000 barrel tank barges and three 1320 horsepower inland towboats. The average age of the 13 inland tank barges was five years. The 13 tank barges transport petrochemicals and refined petroleum products on the Mississippi River System and the Gulf Intracoastal Waterway. As a result of the acquisition, the Company recorded $67,970,000 of property and $30,000 of intangibles with a weighted average amortization period of two years.

During July 2017, the Company purchased four inland tank barges for $1,450,000 as well as a barge fleeting and marine fueling operation business in Freeport, Texas for $3,900,000. The Company had been leasing the barges prior to purchase.

On October 11, 2016, the Company purchased certain assets of Valley Power Systems, Inc. and Valley Power Systems Northwest, Inc. (collectively “VPS”) for $11,440,000 in cash. The assets purchased are mainly related to the EMD engine supply and repair business of VPS and include an EMD distributor agreement to sell engines in nine western states. As a result of the acquisition, the Company recorded $8,330,000 of goodwill and $2,070,000 of intangibles with a weighted average amortization period of approximately 15 years. The Company expects all of the goodwill to be deductible for tax purposes.

On June 30, 2016, the Company purchased an 80,000 barrel coastal tank barge from TD Equipment Finance, Inc. (“TD Equipment”) for $13,682,000 in cash. The Company had been leasing the barge from TD Equipment prior to its purchase.

On June 2, 2016, the Company purchased four coastal tugboats from Crosby Marine Transportation LLC for $26,450,000 in cash. The four coastal tugboats have an average age of 13 years.

On April 15, 2016, the Company purchased the inland tank barge fleet of SEACOR Holdings Inc. (“Seacor”) from subsidiaries of Seacor for a total value of $89,181,000. The assets purchased consisted of 27 inland 30,000 barrel tank barges and 14 inland towboats. The purchase price was comprised of $85,500,000 in cash and the transfer to Seacor of a Florida-based ship docking tugboat with a value of $3,681,000. The average age of the 27 inland tank barges was ten years. Seacor, through its subsidiary, SCF Waxler Marine LLC, transported refined petroleum products, petrochemicals and black oil on the Mississippi River System and the Gulf Intracoastal Waterway. As a result of the acquisition, the Company recorded $985,000 of goodwill and expects all of the goodwill to be deductible for tax purposes. No intangibles other than goodwill were identified in the acquisition.

Pro forma results of the acquisitions made in 2017 and 2016 have not been presented as the pro forma revenues, earnings before taxes on income, net earnings and net earnings per share would not be materially different from the Company’s actual results.

Impairment of Long-lived Assets	12 Months Ended
Impairment of Long-lived Assets	Dec. 31, 2017
Impairment of Long-lived Assets [Abstract]
Impairment of Long-lived Assets	(3) Impairment of Long-lived Assets During the fourth quarter of 2017, the Company recorded a $105,712,000 non-cash pre-tax impairment charge. The after-tax effect of the charge was $66,975,000 or $1.20 per share. The impairment charge was to reduce certain vessels to a fair value of $12,550,000 as the Company decided to put certain older out-of-service vessels up for sale in its marine transportation segment in response to lower equipment utilization, pricing pressure and expensive ballast water treatment system installations required in the next few years on some of the coastal tank barges. Retiring some of the older coastal marine vessels reduces the fleet’s age profile and improves the efficiency of the fleet. The vessels that the Company has committed to dispose of include 12 out-of-service coastal tank barges 21 inactive coastal tugboats and six inactive inland towboats. The tank barges will be scrapped or sold into international non-competing markets in 2018 and the tugboats and towboats will be sold or scrapped in domestic markets during 2018. The fair market value of the vessels of $12,550,000 is presented in prepaid expenses and other current assets at December 31, 2017.

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2017
Fair Value Measurements [Abstract]
Fair Value Measurements	(5) Fair Value Measurements The accounting guidance for using fair value to measure certain assets and liabilities establishes a three tier value hierarchy, which prioritizes the inputs to valuation techniques used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little, if any, market data exists, therefore requiring an entity to develop its own assumptions about the assumptions that market participants would use in pricing the asset or liability. Cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities have carrying values that approximate fair value due to the short-term maturity of these financial instruments. The fair value of the Company’s debt instruments is described in Note 6, Long-Term Debt. Certain assets are measured at fair value on a nonrecurring basis. These assets are adjusted to fair value when there is evidence of impairment. During the years ended December 31, 2017 and 2016, there was no indication that the Company’s long-lived assets were impaired, and accordingly, measurement at fair value was not required.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Long-Term Debt

12 Months Ended

Dec. 31, 2017

Long-Term Debt [Abstract]

Long-Term Debt

(6) Long-Term Debt

Long-term debt at December 31, 2017 and 2016 consisted of the following (in thousands):

	2017			2016
Long-term debt, including current portion:
$850,000,000 revolving credit facility due June 26, 2022	$	495,845		$	225,986
$150,000,000 senior notes Series A due February 27, 2020		150,000			150,000
$350,000,000 senior notes Series B due February 27, 2023		350,000			350,000
$10,000,000 credit line due June 30, 2019		—			—
Bank notes payable		3			—
		995,848			725,986
Unamortized debt issuance costs		(3,442	)		(3,184	)
	$	992,406		$	722,802

The aggregate payments due on the long-term debt in each of the next five years were as follows (in thousands):

2018	$	3
2019		—
2020		150,000
2021		—
2022		495,845
Thereafter		350,000
	$	995,848

On June 26, 2017, the Company entered into an amendment of its Revolving Credit Facility with a syndicate of banks, with JPMorgan Chase Bank, N.A. as the administrative agent bank, that increased the borrowing limit from $550,000,000 to $850,000,000 and extended the maturity date to June 26, 2022. In addition, the credit agreement allows for a $300,000,000 increase in the aggregate commitments of the banks in the form of revolving credit loans or term loans, subject to the consent of each bank that elects to participate in the increased commitment. The variable interest rate spread varies with the Company’s senior debt rating and is currently 1.00% over the London Interbank Offered Rate (“LIBOR”) or equal to an Alternate Base Rate calculated with reference to the agent bank’s prime rate, among other factors. The commitment fee is currently 0.10%. The Revolving Credit Facility contains certain restrictive financial covenants including an interest coverage ratio and a debt-to-capitalization ratio. In addition to financial covenants, the Revolving Credit Facility contains covenants that, subject to exceptions, restrict debt incurrence, mergers and acquisitions, sales of assets, dividends and investments, liquidations and dissolutions, capital leases, transactions with affiliates and changes in lines of business. Borrowings under the Revolving Credit Facility may be used for general corporate purposes, the purchase of existing or new equipment, the purchase of the Company’s common stock, or for business acquisitions. As of December 31, 2017, the Company was in compliance with all Revolving Credit Facility covenants and had $495,845,000 of debt outstanding under the Revolving Credit Facility. The average borrowing under the Revolving Credit Facility during 2017 was $270,446,000, computing by averaging the daily balance, and the weighted average interest rate was 2.2%, computed by dividing the interest expense under the Revolving Credit Facility by the average Revolving Credit Facility borrowing. The Revolving Credit Facility includes a $25,000,000 commitment which may be used for standby letters of credit. Outstanding letters of credit under the Revolving Credit Facility were $8,893,000 as of December 31, 2017.

The Company has $500,000,000 of unsecured senior notes (“Senior Notes Series A” and “Senior Notes Series B”) with a group of institutional investors, consisting of $150,000,000 of 2.72% Senior Notes Series A due February 27, 2020 and $350,000,000 of 3.29% Senior Notes Series B due February 27, 2023. No principal payments are required until maturity. The Senior Notes Series A and Series B contain certain covenants on the part of the Company, including an interest coverage covenant, a debt-to-capitalization covenant and covenants relating to liens, asset sales and mergers, among others. The Senior Notes Series A and Series B also specify certain events of default, upon the occurrence of which the maturity of the notes may be accelerated, including failure to pay principal and interest, violation of covenants or default on other indebtedness, among others. As of December 31, 2017, the Company was in compliance with all Senior Notes Series A and Series B covenants and had $150,000,000 of Senior Notes Series A outstanding and $350,000,000 of Senior Notes Series B outstanding.

The Company has a $10,000,000 line of credit (“Credit Line”) with Bank of America, N.A. (“Bank of America”) for short-term liquidity needs and letters of credit, with a maturity date of June 30, 2019. The Credit Line allows the Company to borrow at an interest rate agreed to by Bank of America and the Company at the time each borrowing is made or continued. The Company had no borrowings outstanding under the Credit Line as December 31, 2017. Outstanding letters of credit under the Credit Line were $1,117,000 as of December 31, 2017.

On September 13, 2017, as a result of the S&S acquisition, the Company assumed $12,135,000 of term debt which was paid off without penalty in the 2017 fourth quarter.

The Company also had $3,000 of short-term secured loans outstanding, as of December 31, 2017, related to its South American operations.

The estimated fair value of total debt outstanding at December 31, 2017 and 2016 was $984,017,000 and $715,330,000, respectively, which differs from the carrying amount of $992,406,000 and $722,802,000, respectively, included in the consolidated financial statements. The fair value was determined using an income approach that relies on inputs such as yield curves.

Taxes on Income

12 Months Ended

Dec. 31, 2017

Taxes on Income [Abstract]

Taxes on Income

(7) Taxes on Income

Earnings before taxes on income and details of the provision for taxes on income for the years ended December 31, 2017, 2016 and 2015 were as follows (in thousands):

	2017			2016		2015
Earnings (loss) before taxes on income:
United States	$	74,267		$	227,746	$	361,712
Foreign		(1,253	)		—		—
	$	73,014		$	227,746	$	361,712

Provision (benefit) for taxes on income:
U.S. Federal:
Current	$	11,143		$	28,919	$	64,707
Deferred		(258,703	)		49,685		59,582
	$	(247,560	)	$	78,604	$	124,289
U.S. State:
Current	$	3,861		$	4,727	$	6,280
Deferred		2,280			1,611		3,173
	$	6,141		$	6,338	$	9,453
Foreign:
Current	$	370		$	—	$	—
Deferred		160			—		—
	$	530		$	—	$	—
Consolidated:
Current	$	15,374		$	33,646	$	70,987
Deferred		(256,263	)		51,296		62,755
	$	(240,889	)	$	84,942	$	133,742

On December 22, 2017, U.S. federal tax legislation, commonly referred to as the Tax Cuts and Jobs Act (the “Act”), was signed into law with the primary provisions impacting the Company being the reduction of the U.S. corporate income tax rate from 35% to 21% and an increase in bonus tax deprecation for certain assets through 2026. As a result of the Act, the Company recognized a one-time deferred tax benefit of $269,472,000 in the 2017 fourth quarter due to the remeasurement of the Company’s U.S. deferred tax assets and liabilities based on the 21% corporate tax rate.

The Company regards these amounts as provisional amounts as they are based on reasonable estimates of temporary difference changes in 2017 and the Company’s state tax apportionment ratios. The Company expects to adjust these provisional amounts as the Company prepares its 2017 federal and state tax returns. The Company will complete its analysis of the income tax effects of the Act before the end of the measurement period on December 21, 2018.

The Company’s provision for taxes on income varied from the statutory federal income tax rate for the years ended December 31, 2017, 2016 and 2015 due to the following:

	2017			2016			2015
United States income tax statutory rate		35.0	%		35.0	%		35.0	%
State and local taxes, net of federal benefit		0.9			1.8			1.7
Change due to U.S. tax reform		(369.0	)		—			—
Other – net		3.2			0.5			0.3
		(329.9	)%		37.3	%		37.0	%

The tax effects of temporary differences that give rise to significant portions of the non-current deferred tax assets and liabilities at December 31, 2017 and 2016 were as follows (in thousands):

	2017			2016
Non-current deferred tax assets and liabilities:
Deferred tax assets:
Compensated absences	$	432		$	739
Allowance for doubtful accounts		1,875			2,534
Postretirement health care benefits		1,190			2,234
Insurance accruals		4,599			9,128
Deferred compensation		1,849			11,124
Unrealized loss on defined benefit plans		11,097			28,832
Operating loss carryforwards		15,540			7,846
Pension benefits		549			—
Other		18,474			25,735
		55,605			88,172
Valuation allowances		(15,308	)		(7,417	)
		40,297			80,755
Deferred tax liabilities:
Property		(428,947	)		(654,751	)
Deferred state taxes		(58,366	)		(54,812	)
Pension benefits		—			(2,799	)
Goodwill and other intangibles		(9,015	)		(51,551	)
Other		(12,420	)		(22,295	)
		(508,748	)		(786,208	)
	$	(468,451	)	$	(705,453	)

The Company has determined that it is more likely than not that all federal deferred tax assets at December 31, 2017 will be realized, including its operating loss carryforwards of $232,000 that expire in various amounts through 2030.

The valuation allowance for state deferred tax assets as of December 31, 2017 and 2016 was $9,289,000 and $7,417,000, respectively, related to the Company’s state net operating loss carryforwards based on the Company’s determination that it is more likely than not that the deferred tax assets will not be realized. Expiration of these state net operating loss carryforwards vary by state through 2037 and none will expire in fiscal 2018.

As of December 31, 2017, the Company had a gross Canadian net operating loss carryforward of $6,019,000 which expires in 2038. A full valuation allowance has been provided for this asset.

The Company or one of its subsidiaries files income tax returns in the United States federal jurisdiction and various state jurisdictions. The Company is currently open to audit under the statute of limitations by the Internal Revenue Service for the 2014 through 2016 tax years. With few exceptions, the Company and its subsidiaries’ state income tax returns are open to audit under the statute of limitations for the 2011 through 2016 tax years.

As of December 31, 2017, the Company has provided a liability of $2,462,000 for unrecognized tax benefits related to various income tax issues which includes interest and penalties. The amount that would impact the Company’s effective tax rate, if recognized, is $1,947,000, with the difference between the total amount of unrecognized tax benefits and the amount that would impact the effective tax rate being primarily related to the federal tax benefit of state income tax items. It is not reasonably possible to determine if the liability for unrecognized tax benefits will significantly change prior to December 31, 2018 due to the uncertainty of possible examination results.

A reconciliation of the beginning and ending amount of the liability for unrecognized tax benefits for the years ended December 31, 2017, 2016 and 2015, is as follows (in thousands):

	2017			2016			2015
Balance at beginning of year	$	2,019		$	1,958		$	1,171
Additions based on tax positions related to the current year		403			187			339
Additions for tax positions of prior years		273			867			785
Reductions for tax positions of prior years		(908	)		(441	)		(337	)
Settlements		—			(552	)		—
Balance at end of year	$	1,787		$	2,019		$	1,958

The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for federal and state income taxes. The Company recognized net expense of $120,000, $88,000 and $216,000 in interest and penalties for the years ended December 31, 2017, 2016 and 2015, respectively. The Company had $675,000, $554,000 and $522,000 of accrued liabilities for the payment of interest and penalties at December 31, 2017, 2016 and 2015, respectively.

Leases

12 Months Ended

Dec. 31, 2017

Leases [Abstract]

Leases

(8) Leases

The Company and its subsidiaries currently lease various facilities and equipment under a number of cancelable and noncancelable operating leases. Lease agreements for barges have terms from one to 12 years expiring at various dates through 2023. Lease agreements for towing vessels chartered by the Company have terms from 30 days to ten years expiring at various dates through 2027; however, approximately 75% of the towing vessel charter agreements are for terms of one year or less. Total rental expense for the years ended December 31, 2017, 2016 and 2015 was as follows (in thousands):

	2017		2016		2015
Rental expense:
Marine equipment — barges	$	11,550	$	13,791	$	14,092
Marine equipment — towing vessels		116,690		137,609		143,067
Other buildings and equipment		15,915		11,182		9,383
Rental expense	$	144,155	$	162,582	$	166,542

Future minimum lease payments under operating leases that have initial or remaining noncancelable lease terms in excess of one year at December 31, 2017 were as follows (in thousands):

	Land, Buildings		Marine Equipment
	And Equipment		Barges		Towing Vessels		Total
2018	$	18,888	$	8,711	$	59,185	$	86,784
2019		15,153		4,573		8,727		28,453
2020		12,432		3,806		2,578		18,816
2021		11,384		1,567		2,578		15,529
2022		9,436		1,567		2,578		13,581
Thereafter		73,382		896		12,889		87,167
	$	140,675	$	21,120	$	88,535	$	250,330

Stock Award Plans

12 Months Ended

Dec. 31, 2017

Stock Award Plans [Abstract]

Stock Award Plans

(9) Stock Award Plans

The Company has share-based compensation plans which are described below. The compensation cost that has been charged against earnings for the Company’s stock award plans and the income tax benefit recognized in the statement of earnings for stock awards for the years ended December 31, 2017, 2016 and 2015 were as follows (in thousands):

	2017		2016		2015
Compensation cost	$	11,460	$	11,675	$	11,104
Income tax benefit	$	4,333	$	4,378	$	4,120

The Company has an employee stock award plan for selected officers and other key employees which provide for the issuance of stock options, restricted stock and performance awards. The exercise price for each option equals the fair market value per share of the Company’s common stock on the date of grant. Substantially all stock options outstanding under the plan have terms of seven years and vest ratably over three years. No performance awards payable in stock have been awarded under the plan. At December 31, 2017, 1,805,296 shares were available for future grants under the employee plan and no outstanding stock options under the employee plan were issued with stock appreciation rights.

The following is a summary of the stock option activity under the employee plan described above for the years ended December 31, 2017, 2016 and 2015:

	Outstanding Non- Qualified or Nonincentive Stock Awards			Weighted Average Exercise Price
Outstanding at December 31, 2014		322,956		$	69.95
Granted		114,894		$	74.99
Canceled or expired		(7,418	)	$	86.28
Outstanding at December 31, 2015		430,432		$	71.01
Granted		186,706		$	53.50
Canceled or expired		(16,017	)	$	80.17
Outstanding at December 31, 2016		601,121		$	65.33
Granted		123,141		$	68.46
Exercised		(36,616	)	$	47.95
Canceled or expired		(32,991	)	$	74.07
Outstanding at December 31, 2017		654,655		$	66.45

Under the employee plan, stock options exercisable were 380,608, 321,942 and 239,518 at December 31, 2017, 2016 and 2015, respectively.

The following table summarizes information about the Company’s outstanding and exercisable stock options under the employee plan at December 31, 2017:

		Options Outstanding								Options Exercisable
Range of Exercise Prices		Number Outstanding		Weighted Average Remaining Contractual Life in Years		Weighted Average Exercise Price		Aggregated Intrinsic Value		Number Exercisable		Weighted Average Exercise Price		Aggregated Intrinsic Value
$	46.74 – $51.23		197,776		3.8	$	50.02				100,806	$	48.86
$	64.65 – $74.99		394,704		4.0	$	69.68				217,627	$	70.25
$	93.64 – $96.85		33,987		3.1	$	94.31				33,987	$	94.31
$	101.46 – $104.37		28,188		3.2	$	102.88				28,188	$	102.88
$	46.74 – $104.37		654,655		3.8	$	66.45	$	3,455,000		380,608	$	69.15	$	1,883,000

The following is a summary of the restricted stock award activity under the employee plan described above for the years ended December 31, 2017, 2016 and 2015:

	Unvested Restricted Stock Award Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested balance at December 31, 2014		321,453		$	71.04
Granted		122,740		$	75.04
Vested		(113,958	)	$	60.73
Forfeited		(18,508	)	$	82.00
Nonvested balance at December 31, 2015		311,727		$	75.73
Granted		190,610		$	53.56
Vested		(105,109	)	$	69.93
Forfeited		(19,573	)	$	76.06
Nonvested balance at December 31, 2016		377,655		$	66.14
Granted		127,255		$	68.50
Vested		(105,600	)	$	68.91
Forfeited		(35,189	)	$	69.45
Nonvested balance at December 31, 2017		364,121		$	65.84

The Company has a stock award plan for nonemployee directors of the Company which provides for the issuance of stock options and restricted stock. The director plan provides for automatic grants of restricted stock to nonemployee directors after each annual meeting of stockholders. In addition, the director plan allows for the issuance of stock options or restricted stock in lieu of cash for all or part of the annual director fee at the option of the director. The exercise prices for all options granted under the plan are equal to the fair market value per share of the Company’s common stock on the date of grant. The terms of the options are ten years. The restricted stock issued after each annual meeting of stockholders vests six months after the date of grant. Options granted and restricted stock issued in lieu of cash director fees vest in equal quarterly increments during the year to which they relate. At December 31 2017, 510,071 shares were available for future grants under the director plan. The director stock award plan is intended as an incentive to attract and retain qualified independent directors.

The following is a summary of the stock option activity under the director plan described above for the years ended December 31, 2017, 2016, and 2015:

	Outstanding Non- Qualified or Nonincentive Stock Awards			Weighted Average Exercise Price
Outstanding at December 31, 2014		298,334		$	60.01
Exercised		(77,905	)	$	47.65
Outstanding at December 31, 2015		220,429		$	64.37
Exercised		(9,000	)	$	35.72
Canceled or expired		(6,000	)	$	99.52
Outstanding at December 31, 2016		205,429		$	64.60
Granted		3,188		$	70.65
Exercised		(39,000	)	$	46.23
Canceled or expired		(12,000	)	$	87.35
Outstanding at December 31, 2017		157,617		$	67.54

Under the director plan, options exercisable were 156,820, 205,429 and 220,429 at December 31, 2017, 2016 and 2015, respectively.

The following table summarizes information about the Company’s outstanding and exercisable stock options under the director plan at December 31, 2017:

		Options Outstanding								Options Exercisable
Range of Exercise Prices		Number Outstanding		Weighted Average Remaining Contractual Life in Years		Weighted Average Exercise Price		Aggregate Intrinsic Value		Number Exercisable		Weighted Average Exercise Price		Aggregate Intrinsic Value
$	29.60		6,000		1.3	$	29.60				6,000	$	29.60
$	41.24 – $56.45		53,276		2.4	$	52.77				53,276	$	52.77
$	61.89 – $62.48		35,153		4.5	$	62.31				35,153	$	62.31
$	70.65 – $99.52		63,188		6.0	$	86.50				62,391	$	86.71
$	29.60 – $99.52		157,617		4.3	$	67.54	$	1,128,000		156,820	$	67.52	$	1,128,000

The following is a summary of the restricted stock award activity under the director plan described above for the years ended December 31, 2017, 2016 and 2015:

	Unvested Restricted Stock Award Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested balance at December 31, 2014		292		$	99.52
Granted		20,350		$	78.52
Vested		(18,851	)	$	79.77
Nonvested balance at December 31, 2015		1,791		$	68.73
Granted		23,074		$	64.89
Vested		(24,518	)	$	65.17
Nonvested balance at December 31, 2016		347		$	64.89
Granted		21,198		$	70.65
Vested		(21,226	)	$	70.56
Nonvested balance at December 31, 2017		319		$	70.65

The total intrinsic value of all stock options exercised under all of the Company’s plans was $1,671,000, $266,000 and $2,555,000 for the years ended December 31, 2017, 2016 and 2015, respectively. The actual tax benefit realized for tax deductions from stock option exercises was $632,000, $100,000 and $948,000 for the years ended December 31, 2017, 2016 and 2015, respectively.

The total intrinsic value of all the restricted stock vestings under all of the Company’s plans was $8,485,000, $6,928,000 and $10,270,000 for the years ended December 31, 2017, 2016 and 2015, respectively. The actual tax benefit realized for tax deductions from restricted stock vestings was $3,208,000, $2,598,000 and $3,810,000 for the years ended December 31, 2017, 2016 and 2015, respectively.

As of December 31, 2017, there was $3,092,000 of unrecognized compensation cost related to nonvested stock options and $16,947,000 related to restricted stock. The stock options are expected to be recognized over a weighted average period of approximately 1.3 years and restricted stock over approximately 3.0 years. The total fair value of stock options vested was $2,530,000, $2,495,000 and $2,180,000 during the years ended December 31, 2017, 2016 and 2015, respectively. The fair value of the restricted stock vested was $8,485,000, $6,928,000 and $10,270,000 for the years ended December 31, 2017, 2016 and 2015, respectively.

The weighted average per share fair value of stock options granted during the years ended December 31, 2017, 2016 and 2015 was $20.72, $17.30 and $25.18, respectively. The fair value of the stock options granted during the years ended December 31, 2017, 2016 and 2015 was $2,617,000, $3,231,000 and $2,893,000, respectively. The Company currently uses treasury stock shares for restricted stock grants and stock option exercises. The fair value of each stock option was determined using the Black-Scholes option pricing model. The key input variables used in valuing the stock options during the years ended December 31, 2017, 2016 and 2015 were as follows:

	2017			2016			2015
Dividend yield	None			None			None
Average risk-free interest rate		2.0	%		1.5	%		1.3	%
Stock price volatility		27	%		30	%		33	%
Estimated option term	Six years			Six years			Six years

Retirement Plans

12 Months Ended

Dec. 31, 2017

Retirement Plans [Abstract]

Retirement Plans

(10) Retirement Plans

The Company sponsors a defined benefit plan for its inland vessel personnel and shore based tankermen. The plan benefits are based on an employee’s years of service and compensation. The plan assets consist primarily of equity and fixed income securities.

On April 12, 2017, the Company amended its pension plan to cease all benefit accruals for periods after May 31, 2017 for certain participants. Participants grandfathered and not impacted were those, as of the close of business on May 31, 2017, who either (a) had completed 15 years of pension service or (b) had attained age 50 and completed 10 years of pension service. Participants non-grandfathered are eligible to receive discretionary 401(k) plan contributions. The Company did not incur any one-time charges related to this amendment but the pension plan’s projected benefit obligation decreased by $33,433,000.

The fair value of plan assets was $294,995,000 and $257,517,000 at December 31, 2017 and 2016 respectively. As of December 31, 2017 and 2016, these assets were allocated among asset categories as follows:

Asset Category	2017			2016			Current Minimum, Target and Maximum Allocation Policy
U.S. equity securities		51	%		51	%		30% — 50%— 70	%
International equity securities		21	%		19	%		0% — 20%— 30	%
Debt securities		28	%		30	%		15% — 30%— 55	%
Cash and cash equivalents		—	%		—	%		0% — 0%— 5	%
		100	%		100	%

The plan assets are invested entirely in common collective trusts. These instruments are public investment vehicles valued using the net asset value provided by the administrator of the fund. The net asset value is classified within Level 2 of the valuation hierarchy as set forth in the accounting guidance for fair value measurements because the net asset value price is quoted on an inactive private market although the underlying investments are traded on an active market.

The Company’s investment strategy focuses on total return on invested assets (capital appreciation plus dividend and interest income). The primary objective in the investment management of assets is to achieve long-term growth of principal while avoiding excessive risk. Risk is managed through diversification of investments within and among asset classes, as well as by choosing securities that have an established trading and underlying operating history.

The Company makes various assumptions when determining defined benefit plan costs including, but not limited to, the current discount rate and the expected long-term return on plan assets. Discount rates are determined annually and are based on a yield curve that consists of a hypothetical portfolio of high quality corporate bonds with maturities matching the projected benefit cash flows. The Company assumed that plan assets would generate a long-term rate of return of 7.0% in 2017 and 2016. The Company developed its expected long-term rate of return assumption by evaluating input from investment consultants comparing historical returns for various asset classes with its actual and targeted plan investments. The Company believes that its long-term asset allocation, on average, will approximate the targeted allocation.

The Company’s pension plan funding strategy is to make annual contributions in amounts equal to or greater than amounts necessary to meet minimum government funding requirements. The plan's benefit obligations are based on a variety of demographic and economic assumptions, and the pension plan assets’ returns are subject to various risks, including market and interest rate risk, making an accurate prediction of the pension plan contribution difficult. The Company’s pension plan funding was 91% of the pension plan’s ABO at December 31, 2017.

The Company sponsors an unfunded defined benefit health care plan that provides limited postretirement medical benefits to employees who met minimum age and service requirements, and to eligible dependents. The plan limits cost increases in the Company’s contribution to 4% per year. The plan is contributory, with retiree contributions adjusted annually. The plan eliminated coverage for future retirees as of December 31, 2011. The Company also has an unfunded defined benefit supplemental executive retirement plan (“SERP”) that was assumed in an acquisition in 1999. That plan ceased to accrue additional benefits effective January 1, 2000.

The following table presents the change in benefit obligation and plan assets for the Company’s defined benefit plans and postretirement benefit plan (in thousands):

															Other Postretirement Benefits
	Pension Benefits														Postretirement
	Pension Plan								SERP						Welfare Plan
	2017				2016				2017			2016			2017			2016
Change in benefit obligation
Benefit obligation at beginning of year		$	337,176			$	297,325		$	1,457		$	1,526		$	675		$	891
Service cost			10,677				13,402			—			—			—			—
Interest cost			13,729				14,123			58			65			27			29
Actuarial loss (gain)			34,563				19,120			42			12			52			(198	)
Curtailments			(33,433	)			—			—			—			—			—
Gross benefits paid			(7,718	)			(6,794	)		(145	)		(146	)		(75	)		(47	)
Benefit obligation at end of year		$	354,994			$	337,176		$	1,412		$	1,457		$	679		$	675

Accumulated benefit obligation at end of year		$	324,904			$	272,591		$	1,412		$	1,457		$	679		$	675

Weighted-average assumption used to determine benefit obligation at end of year
Discount rate		3.7	%		4.2	%	3.7	%	4.2	%	3.7	%	4.2	%
Rate of compensation increase	Service-based table			Service- based table			—		—		—		—
Health care cost trend rate
Initial rate		—			—		—		—		7.0	%	7.0	%
Ultimate rate		—			—		—		—		5.0	%	5.0	%
Years to ultimate		—			—		—		—		2022		2021


Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation
Increase	$	—	$	—	$	—	$	—	$	75		$	74
Decrease		—		—		—		—		(65	)		(64	)

Change in plan assets
Fair value of plan assets at beginning of year	$	257,517		$	243,588		$	—		$	—		$	—		$	—
Actual return on plan assets		45,196			20,723			—			—			—			—
Employer contribution		—			—			145			146			75			47
Gross benefits paid		(7,718	)		(6,794	)		(145	)		(146	)		(75	)		(47	)
Fair value of plan assets at end of year	$	294,995		$	257,517		$	—		$	—		$	—		$	—

The following table presents the funded status and amounts recognized in the Company’s consolidated balance sheet for the Company’s defined benefit plans and postretirement benefit plan at December 31, 2017 and 2016 (in thousands):

													Other Postretirement Benefits
	Pension Benefits												Postretirement Welfare Plan
	Pension Plan						SERP						Postretirement Welfare Plan
	2017			2016			2017			2016			2017			2016
Funded status at end of year
Fair value of plan assets	$	294,995		$	257,517		$	—		$	—		$	—		$	—
Benefit obligations		(354,994	)		(337,176	)		(1,412	)		(1,457	)		(679	)		(675	)
Funded status and amount recognized at end of year	$	(59,999	)	$	(79,659	)	$	(1,412	)	$	(1,457	)	$	(679	)	$	(675	)

Amounts recognized in the consolidated balance sheets
Noncurrent asset	$	—		$	—		$	—		$	—		$	—		$	—
Current liability		—			—			(159	)		(150	)		(54	)		(56	)
Long-term liability		(59,999	)		(79,659	)		(1,253	)		(1,307	)		(625	)		(619	)

Amounts recognized in accumulated other comprehensive income
Net actuarial loss (gain)	$	57,387	$	87,658	$	508	$	494	$	(5,053	)	$	(5,773	)
Prior service cost (credit)		—		—		—		—		—			—
Accumulated other compensation income	$	57,387	$	87,658	$	508	$	494	$	(5,053	)	$	(5,773	)

The projected benefit obligation and fair value of plan assets for pension plans with a projected benefit obligation in excess of plan assets at December 31, 2017 and 2016 were as follows (in thousands):

	Pension Benefits
	Pension Plan				SERP
	2017		2016		2017		2016
Projected benefit obligation in excess of plan assets
Projected benefit obligation at end of year	$	354,994	$	337,176	$	1,412	$	1,457
Fair value of plan assets at end of year		294,995		257,517		—		—

The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for pension plans with an accumulated benefit obligation in excess of plan assets at December 31, 2017 and 2016 were as follows (in thousands):

	Pension Benefits
	Pension Plan				SERP
	2017		2016		2017		2016
Accumulated benefit obligation in excess of plan assets
Projected benefit obligation at end of year	$	354,994	$	337,176	$	1,412	$	1,457
Accumulated benefit obligation at end of year		324,904		272,591		1,412		1,457
Fair value of plan assets at end of year		294,995		257,517		—		—

The following tables presents the expected cash flows for the Company’s defined benefit plans and postretirement benefit plan at December 31, 2017 and 2016 (in thousands):

									Other Postretirement Benefits
	Pension Benefits								Postretirement
	Pension Plan				SERP				Welfare Plan
	2017		2016		2017		2016		2017		2016
Expected employer contributions
First year	$	—	$	—	$	162	$	153	$	48	$	50

									Other Postretirement Benefits
	Pension Benefits								Postretirement
	Pension Plan				SERP				Welfare Plan
	2017		2016		2017		2016		2017		2016
Expected benefit payments (gross)
Year one	$	9,483	$	8,032	$	162	$	153	$	55	$	58
Year two		10,131		8,835		159		157		56		58
Year three		10,818		9,646		156		155		58		58
Year four		11,608		10,400		152		151		58		58
Year five		12,377		11,201		149		148		46		57
Next five years		75,717		70,419		462		514		214		199

									Other Postretirement Benefits
	Pension Benefits								Postretirement
	Pension Plan				SERP				Welfare Plan
	2017		2016		2017		2016		2017			2016
Expected federal subsidy
Year one	$	—	$	—	$	—	$	—	$	(7	)	$	(7	)
Year two		—		—		—		—		(6	)		(7	)
Year three		—		—		—		—		(6	)		(7	)
Year four		—		—		—		—		(6	)		(7	)
Year five		—		—		—		—		(7	)		(7	)
Next five years		—		—		—		—		(30	)		(33	)

The components of net periodic benefit cost and other changes in plan assets and benefit obligations recognized in other comprehensive income for the Company’s defined benefit plans for the years ended December 31, 2017, 2016 and 2015 were as follows (in thousands):

	Pension Benefits
	Pension Plan									SERP
	2017			2016			2015			2017		2016		2015
Components of net periodic benefit cost
Service cost	$	10,677		$	13,402		$	14,683		$	—	$	—	$	—
Interest cost		13,729			14,123			13,302			58		65		64
Expected return on plan assets		(18,195	)		(16,805	)		(17,921	)		—		—		—
Amortization:
Actuarial loss		4,400			5,484			7,728			28		26		28
Prior service credit		—			—			—			—		—		—
Net periodic benefit cost		10,611			16,204			17,792			86		91		92

Other changes in plan assets and benefit obligations recognized in other comprehensive income
Current year actuarial loss (gain)		7,562			15,203			(19,127	)		42			12			(30	)
Recognition of actuarial loss		(37,833	)		(5,484	)		(7,728	)		(28	)		(26	)		(28	)
Recognition of prior service credit		—			—			—			—			—			—
Total recognized in other comprehensive income		(30,271	)		9,719			(26,855	)		14			(14	)		(58	)

Total recognized in net periodic benefit cost and other comprehensive income	$	(19,660	)	$	25,923		$	(9,063	)	$	100		$	77		$	34

Weighted average assumptions used to determine net periodic benefit cost
Discount rate (1)		4.2/4.0	%		4.5	%	4.1	%	4.2	%	4.5	%	4.1	%
Expected long-term rate of return on plan assets		7.0	%		7.0	%	7.5	%	—		—		—
Rate of compensation increase	Service- based table			Service- based table			4.25	%	—		—		—

(1)

The 2017 benefit cost for the pension plan was determined using a discount rate of 4.2% for the period beginning January 1, 2017 and ending April 11, 2017 and 4.0% for the period beginning April 12, 2017 and ending December 31, 2017.

The estimated amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2018 are as follows (in thousands):

	Pension Benefits
	Pension Plan		SERP
Actuarial loss	$	2,820	$	23
Prior service credit		—		—
	$	2,820	$	23

The components of net periodic benefit cost and other changes in benefit obligations recognized in other comprehensive income for the Company’s postretirement benefit plan for the years ended December 31, 2017, 2016 and 2015 were as follows (in thousands):

	Other Postretirement Benefits
	Postretirement Welfare Plan
	2017			2016			2015
Components of net periodic benefit cost
Service cost	$	—		$	—		$	—
Interest cost		27			29			36
Amortization:
Actuarial gain		(668	)		(747	)		(793	)
Prior service cost		—			—			—
Net periodic benefit cost		(641	)		(718	)		(757	)

Other changes in benefit obligations recognized in other comprehensive income
Current year actuarial gain		52		(198	)		(322	)
Recognition of actuarial gain		668		747			793
Recognition of prior service cost		—		—			—
Adjustment for actual Medicare Part D reimbursement		—		(3	)		(3	)
Total recognized in other comprehensive income		720		546			468

Total recognized in net periodic benefit cost and other comprehensive income	$	79	$	(172	)	$	(289	)

Weighted average assumptions used to determine net periodic benefit cost
Discount rate	4.2	%	4.5	%	4.1	%
Health care cost trend rate:
Initial rate	7.0	%	6.5	%	7.0	%
Ultimate rate	5.0	%	5.0	%	5.0	%
Years to ultimate	2021		2019		2019

Effect of one-percentage-point change in assumed health care cost trend rate on aggregate service and interest cost
Increase	$	3		$	4		$	5
Decrease		(3	)		(3	)		(4	)

The estimated amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2018 are as follows (in thousands):

	Other Postretirement Benefits
	Postretirement Welfare Plan
Actuarial gain	$	(596	)
Prior service cost		—
	$	(596	)

The Company also contributes to a multiemployer pension plan pursuant to a collective bargaining agreement which covers certain vessel crew members of its coastal operations and expires on April 30, 2018. The Company began participation in the Seafarers Pension Trust (“SPT”) with the Penn Maritime, Inc. acquisition on December 14, 2012.

Contributions to the SPT are made currently based on a per day worked basis and charged to expense as incurred and included in costs of sales and operating expenses in the consolidated statement of earnings. During 2017 and 2016, the Company made contributions of $896,000 and $877,000, respectively, to the SPT. The Company’s contributions to the SPT exceeded 5% of total contributions to the SPT in 2016. Total contributions for 2017 are not yet available. The Company did not pay any material surcharges in 2016 or 2017.

The federal identification number of the SPT is 13-6100329 and the Certified Zone Status is Green at December 31, 2016. The Company’s future minimum contribution requirements under the SPT are unavailable because actuarial reports for the 2017 plan year are not yet complete and such contributions are subject to negotiations between the employers and the unions. The SPT was not in endangered or critical status for the 2016 plan year, the latest period for which a report is available, as the funded status was in excess of 100%. Based on an actuarial valuation performed as of December 31, 2016, there would be no withdrawal liability if the Company chose to withdraw from the SPT although the Company currently has no intention of terminating its participation in the SPT.

The Company also contributes to a multiemployer pension plan pursuant to a collective bargaining agreement which covers certain employees of its distribution and services segment in New Jersey and expires on October 8, 2023. The Company began participation in the Central Pension Fund of the International Union of Operating Engineers and Participating Employers (“CPF”) with the S&S acquisition on September 13, 2017.

Contributions to the CPF are made currently based on a fixed hourly rate for each hour worked or paid basis (in some cases contributions are made as a percentage of gross pay) and charged to expense as incurred and included in costs of sales and operating expenses in the consolidated statement of earnings. During 2017, the Company made contributions of $238,000 to the CPF. Total contributions for the 2017 plan year are not yet available. The Company did not pay any material surcharges in 2017.

The federal identification number of the CPF is 36-6052390 and the Certified Zone Status is Green at January 31, 2017. The Company’s future minimum contribution requirements under the CPF are unavailable because actuarial reports for the 2017 plan year, which ended January 31, 2018, are not yet complete and such contributions are subject to negotiations between the employers and the unions. The CPF was not in endangered or critical status for the 2016 plan year, the latest period for which a report is available, as the funded status was 94%. Based on an actuarial valuation performed as of January 31, 2016, there would be no withdrawal liability if the Company chose to withdraw from the CPF although the Company currently has no intention of terminating its participation in the CPF.

In addition to the defined benefit plans, the Company sponsors various defined contribution plans for substantially all employees. The aggregate contributions to the plans were $17,247,000, $18,213,000 and $24,077,000 in 2017, 2016 and 2015, respectively.

Other Comprehensive Income

12 Months Ended

Dec. 31, 2017

Other Comprehensive Income [Abstract]

Other Comprehensive Income

(11) Other Comprehensive Income

The Company’s changes in other comprehensive income for the years ended December 31, 2017, 2016 and 2015 were as follows (in thousands):

	2017									2016									2015
	Gross Amount			Income Tax (Provision) Benefit			Net Amount			Gross Amount			Income Tax (Provision) Benefit			Net Amount			Gross Amount		Income Tax (Provision) Benefit			Net Amount
Pension and postretirement benefits (a):
Amortization of net actuarial loss	$	3,760		$	(1,417	)	$	2,343		$	4,763		$	(1,825	)	$	2,938		$	6,963	$	(2,667	)	$	4,296
Actuarial gains (losses)		25,776			(9,371	)		16,405			(15,013	)		5,754			(9,259	)		19,482		(7,456	)		12,026

Foreign currency translation adjustments		(146	)		—			(146	)		—			—			—			29		—			29

Total	$	29,390		$	(10,788	)	$	18,602		$	(10,250	)	$	3,929		$	(6,321	)	$	26,474	$	(10,123	)	$	16,351

(a)	Actuarial gains (losses) are amortized into costs of sales and operating expenses or selling, general and administrative expenses as appropriate. (See Note 10 – Retirement Plans)

Earnings Per Share

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Earnings Per Share

(12) Earnings Per Share

The following table presents the components of basic and diluted earnings per share for the years ended December 31, 2017, 2016 and 2015 (in thousands, except per share amounts):

	2017			2016			2015
Net earnings attributable to Kirby	$	313,187		$	141,406		$	226,684
Undistributed earnings allocated to restricted shares		(2,213	)		(999	)		(1,345	)
Income available to Kirby common stockholders — basic		310,974			140,407			225,339
Undistributed earnings allocated to restricted shares		2,213			999			1,345
Undistributed earnings reallocated to restricted shares		(2,211	)		(997	)		(1,343	)
Income available to Kirby common stockholders — diluted	$	310,976		$	140,409		$	225,341

Shares outstanding:
Weighted average common stock issued and outstanding		55,702			53,834			55,056
Weighted average unvested restricted stock		(394	)		(380	)		(327	)
Weighted average common stock outstanding — basic		55,308			53,454			54,729
Dilutive effect of stock options		53			58			97
Weighted average common stock outstanding — diluted		55,361			53,512			54,826
Net earnings per share attributable to Kirby common stockholders:
Basic	$	5.62		$	2.63		$	4.12

Diluted	$	5.62		$	2.62		$	4.11

Certain outstanding options to purchase approximately 472,000, 240,000 and 227,000 shares of common stock were excluded in the computation of diluted earnings per share as of December 31, 2017, 2016 and 2015, respectively, as such stock options would have been antidilutive.

Quarterly Results (Unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Results (Unaudited) [Abstract]

Quarterly Results (Unaudited)

(13) Quarterly Results (Unaudited)

The unaudited quarterly results for the year ended December 31, 2017 were as follows (in thousands, except per share amounts):

	Three Months Ended
	March 31, 2017			June 30, 2017			September 30, 2017			December 31, 2017
Revenues	$	491,705		$	473,328		$	541,274		$	708,111
Costs and expenses		446,233			425,708			487,753			755,990
Gain (loss) on disposition of assets		99			(139	)		(159	)		(4,288	)
Operating income (loss)		45,571			47,481			53,362			(52,167	)
Other income (expense)		(116	)		(1	)		(113	)		469
Interest expense		(4,457	)		(4,465	)		(5,388	)		(7,162	)
Earnings before taxes on income		40,998			43,015			47,861			(58,860	)
Benefit (provision) for taxes on income		(13,353	)		(17,043	)		(19,072	)		290,357
Net earnings		27,645			25,972			28,789			231,497
Less: Net earnings attributable to noncontrolling interests		(162	)		(194	)		(182	)		(178	)
Net earnings attributable to Kirby	$	27,483		$	25,778		$	28,607		$	231,319

Net earnings per share attributable to Kirby common stockholders:
Basic	$	0.51		$	0.48		$	0.52		$	3.88
Diluted	$	0.51		$	0.48		$	0.52		$	3.87

The unaudited quarterly results for the year ended December 31, 2016 were as follows (in thousands, except per share amounts):

	Three Months Ended
	March 31, 2016			June 30, 2016			September 30, 2016			December 31, 2016
Revenues	$	458,733		$	441,582		$	434,708		$	435,650
Costs and expenses		393,399			374,868			378,400			378,684
Gain (loss) on disposition of assets		67			94			(122	)		(166	)
Operating income		65,401			66,808			56,186			56,800
Other income (expense)		135			179			(120	)		47
Interest expense		(4,193	)		(4,513	)		(4,507	)		(4,477	)
Earnings before taxes on income		61,343			62,474			51,559			52,370
Provision for taxes on income		(22,859	)		(23,365	)		(19,206	)		(19,512	)
Net earnings		38,484			39,109			32,353			32,858
Less: Net earnings attributable to noncontrolling interests		(385	)		(167	)		(343	)		(503	)
Net earnings attributable to Kirby	$	38,099		$	38,942		$	32,010		$	32,355

Net earnings per share attributable to Kirby common stockholders:
Basic	$	0.71		$	0.72		$	0.59		$	0.60
Diluted	$	0.71		$	0.72		$	0.59		$	0.60

Quarterly basic and diluted earnings per share may not total to the full year per share amounts, as the weighted average number of shares outstanding for each quarter fluctuates as a result of the assumed exercise of stock options.

Contingencies and Commitments	12 Months Ended
Contingencies and Commitments	Dec. 31, 2017
Contingencies and Commitments [Abstract]
Contingencies and Commitments	(14) Contingencies and Commitments In 2009, the Company was named a Potentially Responsible Party (“PRP”) in addition to a group of approximately 250 named PRPs under the Comprehensive Environmental Response, Compensation and Liability Act of 1981 (“CERCLA”) with respect to a Superfund site, the Portland Harbor Superfund site (“Portland Harbor”) in Portland, Oregon. The site was declared a Superfund site in December 2000 as a result of historical heavily industrialized use due to manufacturing, shipbuilding, petroleum storage and distribution, metals salvaging, and electrical power generation activities which led to contamination of Portland Harbor, an urban and industrial reach of the lower Willamette River located immediately downstream of downtown Portland. The Company’s involvement arises from four spills at the site after it was declared a Superfund site, as a result of predecessor entities’ actions in the area. To date, there is no information suggesting the extent of the costs or damages to be claimed from the 250 notified PRPs. Based on the nature of the involvement at the Portland Harbor site, the Company believes its potential contribution is de minimis; however, to date neither the Environmental Protection Agency (“EPA”) nor the named PRPs have performed an allocation of potential liability in connection with the site nor have they provided costs and expenses in connection with the site. In January 2015, the Company was named as a defendant in a Complaint filed in the U.S. District Court of the Southern District of Texas, USOR Site PRP Group vs. A&M Contractors, USES, Inc. et al. This is a civil action pursuant to the provisions of CERCLA and the Texas Solid Waste Disposal Act for recovery of past and future response costs incurred and to be incurred by the USOR Site PRP Group for response activities at the U.S. Oil Recovery Superfund Site. The property was a former sewage treatment plant owned by defendant City of Pasadena, Texas from approximately 1945 until it was acquired by U.S. Oil Recovery in January 2009. Throughout its operating life, the U.S. Oil Recovery facility portion of the USOR Site received and performed wastewater pretreatment of municipal and Industrial Class I and Class II wastewater, characteristically hazardous waste, used oil and oily sludges, and municipal solid waste. Associated operations were conducted at the MCC Recycling facility portion of the USOR Site after it was acquired by U.S. Oil Recovery from the City of Pasadena in January 2009. The EPA and the PRP Group entered into an Administrative Settlement Agreement and Order for Remedial Investigation Study (“Study”) in May 2015. The Study has not been completed by EPA to date. The Company filed responsive pleadings in this matter. Based on the nature of the involvement at the USOR Site, the Company believes its potential contribution is de minimis; however, the Study and further review of the Company’s activities at the Site remains ongoing. On October 13, 2016, the Company, as a successor to Hollywood Marine, Inc., was issued a General Notice under CERCLA in which it was named as a PRP for liabilities associated with the SBA Shipyard Site located near Jennings, Louisiana (“Site”). The Site was added to the EPA’s National Priorities List of sites under CERCLA in September 2016. SBA used the facility for construction, repair, retrofitting, sandblasting, and cleaning and painting of barges beginning in 1965. Three barge slips and a dry dock are located off the Mermentau River. The slips were used to dock barges during cleaning or repair. In 2001, a group of PRPs that had been former customers of the SBA Shipyard facility formed an organization called the SSIC Remediation, LLC (hereinafter, “the PRP Group Companies”) to address removal actions at the Site. In 2002, EPA approved an Interim Measures/Removal Action of Hazardous/Principal Threat Wastes at SBA Shipyards, Inc. (pursuant to RCRA Section 3008(h)) that was proposed by SBA Shipyard and the PRP Group Companies. Interim removal activities were conducted from March 2001 through January 2005 under an EPA 2002 Order and Agreement. In September 2012, the Louisiana Department of Environmental Quality requested EPA address the Site under CERCLA authority. The Company, as a successor to Hollywood Marine, Inc., joined the PRP Group Companies. The PRP Group Companies have submitted a draft Study work plan to EPA for their review and comment. Higman Marine, Inc. and affiliated companies ("Higman") was named as a PRP in connection with its activities at the Site. Higman is not a participant in the PRP Group Companies. With respect to the above sites, the Company has recorded reserves, if applicable, for its estimated potential liability for its portion of the EPA’s past costs claim based on information developed to date including various factors such as the Company’s liability in proportion to other responsible parties and the extent to which such costs are recoverable from third parties. On October 13, 2016, the tug Nathan E. Stewart and barge DBL 55, an articulated tank barge and tugboat unit (“ATB”), ran aground at the entrance to Seaforth Channel on Atholone Island, British Columbia. The grounding resulted in a breach of a portion of the Nathan E. Stewart’s fuel tanks causing a discharge of diesel fuel into the water. The USCG and the National Transportation Safety Board (“NTSB”) designated the Company as a party of interest in their investigation as to the cause of the incident. The Canadian authorities including Transport Canada and the Canadian Transportation Safety Board investigated the cause of the incident. The Company is subject to potential claims from third parties as well as the provincial and federal government as a result of the incident. The Company has various insurance policies covering liabilities including pollution, property, marine and general liability and believes that it has satisfactory insurance coverage for the cost of cleanup and salvage operations as well as other potential liabilities arising from the incident. The Company believes it has accrued adequate reserves for the incident and does not expect the incident to have a material adverse effect on its business or financial condition. On March 22, 2014, two tank barges and a towboat (the M/V Miss Susan), owned by Kirby Inland Marine, LP, a wholly owned subsidiary of the Company, were involved in a collision with the M/S Summer Wind on the Houston Ship Channel near Texas City, Texas. The lead tank barge was damaged in the collision resulting in a discharge of intermediate fuel oil from one of its cargo tanks. The USCG and the NTSB named the Company and the Captain of the M/V Miss Susan, as well as the owner and the pilot of the M/S Summer Wind, as parties of interest in their investigation as to the cause of the incident. Sea Galaxy Ltd is the owner of the M/S Summer Wind. The Company is participating in the natural resource damage assessment and restoration process with federal and state government natural resource trustees. The Company believes it has adequate insurance coverage for pollution, marine and other potential liabilities arising from the incident. The Company believes it has accrued adequate reserves for the incident and does not expect the incident to have a material adverse effect on its business or financial condition. In addition, the Company is involved in various legal and other proceedings which are incidental to the conduct of its business, none of which in the opinion of management will have a material effect on the Company’s financial condition, results of operations or cash flows. Management believes that it has recorded adequate reserves and believes that it has adequate insurance coverage or has meritorious defenses for these other claims and contingencies. Certain Significant Risks and Uncertainties. The preparation of financial statements in conformity with United States generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. However, in the opinion of management, the amounts would be immaterial. The customer base of the marine transportation segment includes major industrial petrochemical and chemical manufacturers, refining companies and agricultural chemical manufacturers operating in the United States. During 2017, approximately 75% of marine transportation’s inland revenues were from movements of such products under term contracts, typically ranging from one year to five years, some with renewal options. During 2017, approximately 80% of the marine transportation’s coastal revenues were under term contracts. While the manufacturing and refining companies have generally been customers of the Company for numerous years (some as long as 40 years) and management anticipates a continuing relationship, there is no assurance that any individual contract will be renewed. No single customer of the marine transportation segment accounted for 10% of the Company’s revenues in 2017, 2016 and 2015. Major customers of the distribution and services segment include oilfield service companies, oil and gas operators and producers, inland and offshore barge operators, offshore fishing companies, on-highway transportation companies, mining companies, construction companies, the United States government, and power generation, nuclear and industrial companies. United has maintained continuous exclusive distribution rights for MTU and Allison Transmission products since 1946. United is one of MTU’s top five distributors of MTU off-highway engines in North America with exclusive distribution rights in Oklahoma, Arkansas, Louisiana and Mississippi. In addition, as a distributor of Allison Transmission products, United has distribution rights in Oklahoma, Arkansas and Louisiana. Finally, United is also the distributor for parts service and warranty on Daimler Truck North America (DTNA) engines and related equipment in Oklahoma, Arkansas and Louisiana. S&S is also one of MTU’s top five distributors for off-highway engines with exclusive distribution rights in multiple states. S&S also has authorized exclusive distribution rights for Allison Transmission, Detroit Diesel, Deutz, DTNA, EMD, Rolls Royce Power and Volvo Penta diesel engines in multiple key growth states, primarily through the central, south and eastern parts of the United States and strategically located near major oil and gas fields, marine waterways and on-highway transportation routes. In addition, S&S has long-term relationships with numerous smaller suppliers including Donaldson, Freightliner, Generac and John Deere. Kirby Engine Systems, through Marine Systems and Engine Systems, operates as an authorized EMD distributor throughout the United States. Engine Systems is also the authorized EMD distributor for nuclear power applications worldwide. The relationship with EMD has been maintained for 52 years. The segment also operates factory-authorized full service marine distributorship/dealerships for Cummins, Detroit Diesel and John Deere high-speed diesel engines and Falk, Lufkin and Twin Disc marine gears, as well as an authorized marine dealer for Caterpillar diesel engine in multiple states. The results of the distribution and services segment are largely tied to the industries it serves and, therefore, can be influenced by the cycles of such industries. No single customer of the distribution and services segment accounted for 10% of the Company’s revenues in 2017, 2016 and 2015. Weather can be a major factor in the day-to-day operations of the marine transportation segment. Adverse weather conditions, such as high or low water, tropical storms, hurricanes, tsunamis, fog and ice, can impair the operating efficiencies of the marine fleet. Shipments of products can be delayed or postponed by weather conditions, which are totally beyond the control of the Company. Adverse water conditions are also factors which impair the efficiency of the fleet and can result in delays, diversions and limitations on night passages, and dictate horsepower requirements and size of tows. Additionally, much of the inland waterway system is controlled by a series of locks and dams designed to provide flood control, maintain pool levels of water in certain areas of the country and facilitate navigation on the inland river system. Maintenance and operation of the navigable inland waterway infrastructure is a government function handled by the Army Corps of Engineers with costs shared by industry. Significant changes in governmental policies or appropriations with respect to maintenance and operation of the infrastructure could adversely affect the Company. The Company’s marine transportation segment is subject to regulation by the USCG, federal laws, state laws and certain international conventions, as well as numerous environmental regulations. The Company believes that additional safety, environmental and occupational health regulations may be imposed on the marine industry. There can be no assurance that any such new regulations or requirements, or any discharge of pollutants by the Company, will not have an adverse effect on the Company. The Company’s marine transportation segment competes principally in markets subject to the Jones Act, a federal cabotage law that restricts domestic marine transportation in the United States to vessels built and registered in the United States, and manned and owned by United States citizens. The Jones Act cabotage provisions occasionally come under attack by interests seeking to facilitate foreign flag competition in trades reserved for domestic companies and vessels under the Jones Act. The Company believes that continued efforts will be made to modify or eliminate the cabotage provisions of the Jones Act. If such efforts are successful, certain elements could have an adverse effect on the Company. The Company has issued guaranties or obtained standby letters of credit and performance bonds supporting performance by the Company and its subsidiaries of contractual or contingent legal obligations of the Company and its subsidiaries incurred in the ordinary course of business. The aggregate notional value of these instruments is $21,554,000 at December 31, 2017, including $10,238,000 in letters of credit and $11,316,000 in performance bonds. All of these instruments have an expiration date within four years. The Company does not believe demand for payment under these instruments is likely and expects no material cash outlays to occur in connection with these instruments.

Segment Data

12 Months Ended

Dec. 31, 2017

Segment Data [Abstract]

Segment Data

(15) Segment Data

The Company’s operations are aggregated into two reportable business segments as follows:

Marine Transportation — Provide marine transportation principally by United States flag vessels of liquid cargoes throughout the United States inland waterway system, along all three United States coasts, in Alaska and Hawaii and, to a lesser extent, in United States coastal transportation of dry-bulk cargoes. The principal products transported include petrochemicals, black oil, refined petroleum products and agricultural chemicals.

Distribution and Services — Provides after-market services and parts for engines, transmissions, reduction gears and related equipment used in oilfield service, marine, power generation, mining, on-highway, and other industrial applications. The Company also rents equipment including generators, fork lifts, pumps and compressors for use in a variety of industrial markets, and manufactures and remanufactures oilfield service equipment, including pressure pumping units, for the oilfield service and oil and gas operator and producer markets.

The Company’s two reportable business segments are managed separately based on fundamental differences in their operations. The Company’s accounting policies for the business segments are the same as those described in Note 1, Summary of Significant Accounting Policies. The Company evaluates the performance of its segments based on the contributions to operating income of the respective segments, and before income taxes, interest, gains or losses on disposition of assets, other nonoperating income, noncontrolling interests, accounting changes, and nonrecurring items. Intersegment revenues, based on market-based pricing, of the distribution and services segment from the marine transportation segment of $20,717,000, $24,672,000 and $26,203,000 in 2017, 2016 and 2015, respectively, as well as the related intersegment profit of $2,072,000, $2,467,000 and $2,620,000 in 2017, 2016 and 2015, respectively, have been eliminated from the tables below.

The following table sets forth by reportable segment the revenues, profit or loss, total assets, depreciation and amortization, and capital expenditures attributable to the principal activities of the Company for the years ended December 31, 2017, 2016 and 2015 (in thousands):

	2017			2016			2015
Revenues:
Marine transportation	$	1,324,106		$	1,471,893		$	1,663,090
Distribution and services		890,312			298,780			484,442
	$	2,214,418		$	1,770,673		$	2,147,532
Segment profit (loss):
Marine transportation	$	136,011		$	257,102		$	374,842
Distribution and services		86,585			3,186			18,921
Other		(149,582	)		(32,542	)		(32,051	)
	$	73,014		$	227,746		$	361,712
Total assets:
Marine transportation	$	3,485,099		$	3,613,951		$	3,444,785
Distribution and services		1,567,085			623,268			632,764
Other		75,243			52,676			63,009
	$	5,127,427		$	4,289,895		$	4,140,558
Depreciation and amortization:
Marine transportation	$	178,898		$	184,291		$	175,798
Distribution and services		20,387			12,833			12,498
Other		3,596			3,793			3,944
	$	202,881		$	200,917		$	192,240
Capital expenditures:
Marine transportation	$	165,421		$	217,423		$	311,862
Distribution and services		5,086			5,915			28,907
Other		6,715			7,728			4,706
	$	177,222		$	231,066		$	345,475

The following table presents the details of “Other” segment profit (loss) for the years ended December 31, 2017, 2016 and 2015 (in thousands):

	2017			2016			2015
General corporate expenses	$	(18,150	)	$	(14,966	)	$	(14,773	)
Interest expense		(21,472	)		(17,690	)		(18,738	)
Impairment of long-lived assets		(105,712	)		—			—
Gain (loss) on disposition of assets		(4,487	)		(127	)		1,672
Other income (expense)		239			241			(212	)
	$	(149,582	)	$	(32,542	)	$	(32,051	)

The following table presents the details of “Other” total assets as of December 31, 2017, 2016 and 2015 (in thousands):

	2017		2016		2015
General corporate assets	$	73,353	$	50,054	$	60,919
Investment in affiliates		1,890		2,622		2,090
	$	75,243	$	52,676	$	63,009

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	(16) Related Party Transactions The Company is a 50% owner of The Hollywood Camp, L.L.C. (“The Hollywood Camp”), a company that owns and operates a hunting and fishing facility used by the Company primarily for customer entertainment. The Hollywood Camp allocates lease and lodging expenses to its members based on their usage of the facilities. The Company paid The Hollywood Camp $3,634,000 in 2017, $3,143,000 in 2016 and $2,830,000 in 2015 for its share of facility expenses. The Company is a 50% owner of Bolivar Terminal Co., Inc. (“Bolivar”), a company that provides barge fleeting services (temporary barge storage facilities) in the Houston, Texas area. The Company paid Bolivar $581,000 in 2017, $1,314,000 in 2016 and $895,000 in 2015 for barge fleeting services. Such services were in the ordinary course of business of the Company. The husband of Amy D. Husted, Vice President and General Counsel of the Company, is a partner in the law firm of Strasburger & Price, LLP. The Company paid the law firm $830,000 in 2017, $779,000 in 2016 and $596,000 in 2015 for legal services in connection with matters in the ordinary course of business of the Company.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	(17) Subsequent Events On February 14, 2018, the Company purchased Higman for approximately $419,692,000 in cash, subject to certain post-closing adjustments. Higman’s fleet consisted of 159 inland tank barges, of which two are under construction to be delivered in May 2018 and October 2018, with 4.8 million barrels of capacity, and 75 inland towboats, transporting petrochemicals, black oil, including crude oil and natural gas condensate, and refined petroleum products on the Mississippi River System and the Gulf Intracoastal Waterway. On February 12, 2018, the Company issued $500,000,000 of 4.2% senior unsecured notes due March 1, 2028 (the "2028 Notes"). The Company used the proceeds from the issuance of the 2028 Notes to fund the acquisition of Higman. The remaining net proceeds of the sale of the 2028 Notes will be used for general corporate purposes, including working capital, the repayment of indebtedness and future acquisitions. Interest payments of $10,500,000 are due semi-annually on March 1 and September 1 of each year, with the exception of the first payment on September 1, 2018, which will be $11,550,000. The 2028 Notes are unsecured and rank equally in right of payment with the Company’s other unsecured senior indebtedness.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation. The consolidated financial statements include the accounts of Kirby Corporation and all majority-owned subsidiaries (“the Company”). All investments in which the Company owns 20% to 50% and exercises significant influence over operating and financial policies are accounted for using the equity method. All material intercompany accounts and transactions have been eliminated in consolidation. Certain reclassifications have been made to reflect the current presentation of financial information.
Cash Equivalents	Cash Equivalents. Cash equivalents consist of all short-term, highly liquid investments with maturities of three months or less at date of purchase.
Accounts Receivable	Accounts Receivable. In the normal course of business, the Company extends credit to its customers. The Company regularly reviews the accounts and makes adequate provisions for probable uncollectible balances. It is the Company’s opinion that the accounts have no impairment, other than that for which provisions have been made. Included in accounts receivable as of December 31, 2017 and 2016 were $153,661,000 and $84,453,000, respectively, of accruals for revenues earned which have not been invoiced as of the end of each year. The Company’s marine transportation and distribution and services operations are subject to hazards associated with such businesses. The Company maintains insurance coverage against these hazards with insurance companies. Included in accounts receivable as of December 31, 2017 and 2016 were $66,588,000 and $88,182,000, respectively, of receivables from insurance companies to cover claims in excess of the Company’s deductible.
Concentrations of Credit Risk	Concentrations of Credit Risk. Financial instruments which potentially subject the Company to concentrations of credit risk are primarily trade accounts receivables. The Company’s marine transportation customers include the major oil refining and petrochemical companies. The distribution and services customers are oilfield service companies, oil and gas operators and producers, on-highway transportation companies, marine transportation companies, commercial fishing companies, construction companies, mining companies, power generation companies, and the United States government. The Company regularly reviews its accounts and estimates the amount of uncollectible receivables each period and establishes an allowance for uncollectible amounts. The amount of the allowance is based on the age of unpaid amounts, information about the current financial strength of customers, and other relevant information. Estimates of uncollectible amounts are revised each period, and changes are recorded in the period they become known.
Fair Value of Financial Instruments	Fair Value of Financial Instruments. Cash, accounts receivable, accounts payable and accrued liabilities have carrying values that approximate fair value due to the short-term maturity of these financial instruments. The fair value of the Company’s debt instruments is more fully described in Note 6, Long-Term Debt.
Property, Maintenance and Repairs	Property, Maintenance and Repairs. Property is recorded at cost. Improvements and betterments are capitalized as incurred. Depreciation is recorded on the straight-line method over the estimated useful lives of the individual assets as follows: marine transportation equipment, 5-40 years; buildings, 10-40 years; other equipment, 2-10 years; and leasehold improvements, term of lease. When property items are retired, sold or otherwise disposed of, the related cost and accumulated depreciation are removed from the accounts with any gain or loss on the disposition included in the statement of earnings. Maintenance and repairs on vessels built for use on the inland waterways are charged to operating expense as incurred and includes the costs incurred in United States Coast Guard (“USCG”) inspections unless the shipyard extends the life or improves the operating capacity of the vessel which results in the costs being capitalized.
Drydocking on Ocean-Going Vessels	Drydocking on Ocean-Going Vessels. The Company’s ocean-going vessels are subject to regulatory drydocking requirements after certain periods of time to be inspected, have planned major maintenance performed and be recertified by the American Bureau of Shipping (“ABS”). These recertifications generally occur twice in a five year period. The Company defers the drydocking expenditures incurred on its ocean-going vessels due to regulatory marine inspections by the ABS and amortizes the costs of the shipyard over the period between drydockings, generally 30 or 60 months, depending on the type of major maintenance performed. Drydocking expenditures that extend the life or improve the operating capability of the vessel result in the costs being capitalized. The Company recognized amortization of major maintenance costs of $21,207,000, $19,869,000 and $22,126,000 for the years ended December 31, 2017, 2016 and 2015, respectively, in costs of sales and operating expenses. Routine repairs and maintenance on ocean-going vessels are expensed as incurred. Interest is capitalized on the construction of new ocean-going vessels. Interest expense excludes capitalized interest of $1,731,000, $2,974,000 and $3,026,000 for the years ending December 31, 2017, 2016 and 2015, respectively.
Environmental Liabilities	Environmental Liabilities. The Company expenses costs related to environmental events as they are incurred or when a loss is considered probable and estimable.
Goodwill	Goodwill. The excess of the purchase price over the fair value of identifiable net assets acquired in transactions accounted for as a purchase is included in goodwill. The Company conducted its annual goodwill impairment test at November 30, 2017 and 2016. For 2017 and 2016, the Company noted no impairment of goodwill. The Company will continue to conduct goodwill impairment tests as of November 30 of subsequent years, or whenever events or circumstances indicate that interim impairment testing is necessary. The amount of goodwill impairment, if any, is typically measured based on projected discounted future operating cash flows using an appropriate discount rate. The gross carrying value of goodwill at December 31, 2017 and 2016 was $947,502,000 and $615,598,000, respectively, and accumulated amortization at December 31, 2017 and 2016 was $15,566,000. Accumulated impairment losses were $1,901,000 at December 31, 2017 and 2016. Net goodwill for the marine transportation segment was $387,504,000 and $382,227,000 at December 31, 2017 and 2016, respectively. The increase in net goodwill for the marine transportation segment for 2017 was due to the purchase of a barge fleeting and marine fueling operation, as well as San Jac Marine, LLC (“San Jac”), which are more fully described in Note 2, Acquisitions. Net goodwill for the distribution and services segment was $547,631,000 and $215,904,000 at December 31, 2017 and 2016, respectively. The increase in net goodwill for the distribution and services segment was due to the acquisition of Stewart & Stevenson LLC (“S&S”) in 2017, also more fully described in Note 2, Acquisitions.
Other Intangibles	Other Intangibles. Other intangibles include assets for customer contracts and relationships, distributorship and dealership agreements, trade names and noncompete agreements and liabilities for unfavorable leases. As of December 31, 2017 and 2016, the gross carrying amounts of other intangible assets were $315,983,000 and $158,634,000, respectively, and the accumulated amortization was $83,175,000 and $71,328,000, respectively, resulting in net carrying amounts of $232,808,000 and $87,306,000, respectively. As of December 31, 2017 and 2016, the gross carrying amounts of other intangible liabilities were $7,437,000 and $5,759,000, respectively, and the accumulated amortization was $4,751,000 and $3,949,000, respectively, resulting in net carrying amounts of $2,686,000 and $1,810,000, respectively. The costs of intangible assets and liabilities are amortized to expense in a systematic and rational manner over their estimated useful lives. For the years ended December 31, 2017, 2016 and 2015, the amortization expense for intangibles was $11,296,000, $8,467,000 and $8,526,000, respectively. Estimated amortization expense for amortizable intangible assets and liabilities for the next five years (2018 – 2022) is approximately $17,760,000, $17,395,000, $17,617,000, $17,171,000 and $16,971,000, respectively. As of December 31, 2017, the weighted average amortization period for intangible assets and liabilities was approximately 15 years.
Revenue Recognition	Revenue Recognition. The majority of marine transportation revenue is derived from term contracts, ranging from one to five years, some of which have renewal options, and the remainder is from spot market movements. The majority of the term contracts are for terms of one year. The Company is a provider of marine transportation services for its customers and, in almost all cases, does not assume ownership of the products it transports. A term contract is an agreement with a specific customer to transport cargo from a designated origin to a designated destination at a set rate or at a daily rate. The rate may or may not escalate during the term of the contract, however, the base rate generally remains constant and contracts often include escalation provisions to recover changes in specific costs such as fuel. A spot contract is an agreement with a customer to move cargo from a specific origin to a designated destination for a rate negotiated at the time the cargo movement takes place. Spot contract rates are at the current “market” rate, including fuel, and are subject to market volatility. The Company uses a voyage accounting method of revenue recognition for its marine transportation revenues which allocates voyage revenue based on the percent of the voyage completed during the period. There is no difference in the recognition of revenue between a term contract and a spot contract. Distribution products and services are generally sold based upon purchase orders or preferential service agreements with the customer that include fixed or determinable prices and that do not include right of return or significant post-delivery performance obligations. Parts sales are recognized when title passes upon shipment to customers or when customer-specific acceptance requirements are met. Service revenue is recognized as the service is provided. Revenue from rental agreements is recognized on a straight-line basis over the rental period. Distribution and services manufacturing and assembly projects revenue is reported on the percentage of completion method of accounting using measurements of progress towards completion appropriate for the work performed.
Stock-Based Compensation	Stock-Based Compensation. The Company has share-based compensation plans covering selected officers and other key employees as well as the Company’s Board of Directors. Stock-based grants made under the Company’s stock plans are recorded at fair value on the date of the grant and the cost is recognized ratably over the vesting period of the stock option or restricted stock. Stock option grants are valued at the date of grant as calculated under the Black-Scholes option pricing model. The Company’s stock-based compensation plans are more fully described in Note 9, Stock Award Plans.
Taxes on Income	Taxes on Income. The Company follows the asset and liability method of accounting for income taxes. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date.
Accrued Insurance	Accrued Insurance. Accrued insurance liabilities include estimates based on individual incurred claims outstanding and an estimated amount for losses incurred but not reported (“IBNR”) or fully developed based on past experience. Insurance premiums, IBNR losses and incurred claim losses, in excess of the Company’s deductible for 2017, 2016 and 2015 were $26,195,000, $23,085,000 and $23,737,000, respectively.
Noncontrolling Interests	Noncontrolling Interests. The Company has a majority interest in and is the general partner in several affiliated entities. In situations where losses applicable to the minority interest in the affiliated entities exceed the limited partners’ equity capital, such excess and any further loss attributable to the minority interest is charged against the Company’s interest in the affiliated entities. If future earnings materialize in the respective affiliated entities, the Company’s interest would be credited to the extent of any losses previously absorbed.
Treasury Stock	Treasury Stock. The Company follows the average cost method of accounting for treasury stock transactions.
Impairment of Long-Lived Assets and for Long-Lived Assets to Be Disposed Of	Impairment of Long-lived Assets and for Long-lived Assets to Be Disposed Of. The Company reviews long-lived assets and certain identifiable intangibles for impairment by vessel class whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. Recoverability on marine transportation assets is assessed based on vessel classes, not on individual assets, because identifiable cash flows for individual marine transportation assets are not available. Projecting customer contract volumes allows estimation of future cash flows by projecting pricing and utilization by vessel class but it is not practical to project which individual marine transportation asset will be utilized for any given contract. Because customers do not specify which particular vessel is used, prices are quoted based on vessel classes not individual assets. Nominations of vessels for specific jobs are determined on a day by day basis and are a function of the equipment class required and the geographic position of vessels within that class at that particular time as vessels within a class are interchangeable and provide the same service. The Company’s vessels are mobile assets and equipped to operate in geographic regions throughout the United States and the Company has in the past and expects to continue to move vessels from one region to another when it is necessary due to changing markets and it is economical to do so. Barge vessel classes are based on similar capacities, hull type, and type of product and towing vessels are based on similar hull type and horsepower. Recoverability of the vessel classes is measured by a comparison of the carrying amount of the assets to future net cash flows expected to be generated by the assets. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell.
Accounting Standards	Accounting Standards In February 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-02, “Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the recent federal tax reform legislation. ASU 2018-02 eliminates the stranded tax effects resulting from the recent federal tax reform legislation and will improve the usefulness of information reported to financial statement users. The amendments in ASU 2018-02 will be applied either in the period of adoption or retrospectively to each period (or periods) in which the effect of the change in the recent federal tax reform legislation is recognized. ASU 2018-02 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted, including adoption in any interim period, for which financial statements have not yet been made available for issuance. The Company is currently evaluating the impact, if any, that the adoption of this standard will have on its consolidated financial statements. In March 2017, the FASB issued ASU 2017-07, “Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost” (“ASU 2017-07”) which requires employers to include only the service cost component of net periodic pension cost and net periodic postretirement benefit cost in operating expenses. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations. The standard allows only the service cost component to be eligible for capitalization when applicable. ASU 2017-07 is effective for annual and interim periods beginning after December 15, 2017 with early adoption permitted. This standard shall be applied retrospectively for the presentation of the service cost component and the other components of net periodic pension cost and net periodic postretirement benefit cost in the income statement and prospectively for the capitalization of the service cost benefit in assets. The Company will adopt the provisions of ASU 2017-07 on January 1, 2018 and the Company does not expect the adoption of ASU 2017-07 to have a material impact on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, “Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment” (“ASU 2017-04”) which simplifies the subsequent measurement of goodwill by eliminating Step 2 in the goodwill impairment test that required an entity to perform procedures to determine the fair value of its assets and liabilities at the testing date. An entity instead will perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying value and record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. ASU 2017-04 will be applied prospectively and is effective for annual and interim goodwill impairment tests conducted in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment testing dates after January 1, 2017. The Company is currently evaluating the impact, if any, that the adoption of this standard will have on its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments” (“ASU 2016-15”) to create consistency in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. ASU 2016-15 is effective for annual and interim periods beginning after December 15, 2017. The Company will adopt the provisions of ASU 2016-15 on January 1, 2018 and the Company does not expect the adoption of ASU 2016-15 to have a material impact on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, “Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”) which simplifies several aspects of the accounting for share-based payment transactions, including income tax consequences, forfeitures, minimum statutory tax withholding requirements, classification as either equity or liabilities, and classification on the statement of cash flows. The Company adopted the provisions of ASU 2016-09 on January 1, 2017. ASU 2016-09 requires all excess tax benefits and tax deficiencies be recognized as income tax expense or benefit in the income statement, thus eliminating additional paid-in capital pools. The Company recognized a cumulative effect adjustment of $8,486,000 to retained earnings on a modified retrospective basis as of January 1, 2017 and will apply the new standard guidance prospectively to all excess tax benefits and tax deficiencies resulting from settlements after January 1, 2017. The standard also requires a policy election to either estimate the number of awards that are expected to vest or account for forfeitures when they occur. The Company will elect to account for forfeitures when they occur. Also, the standard requires that excess tax benefits should be classified along with other income tax cash flows as an operating activity on the statement of cash flows, which differs from the Company’s historical classification of excess tax benefits as cash inflows from financing activities. The Company elected to apply this provision using the prospective transition method. Additionally, the standard requires cash paid by an employer when directly withholding shares for tax withholding purposes to be classified in the statement of cash flows as a financing activity, which differs from the Company’s previous method of classification of such cash payments as an operating activity. The Company applied this provision retrospectively and reclassified $1,756,000 and $2,975,000 during 2016 and 2015, respectively, which increased net cash provided by operating activities and net cash used in financing activities. In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842)” (“ASU 2016-02”) to increase transparency and comparability among organizations by requiring recognition of lease assets and lease liabilities on the balance sheet and disclosure of key information about leasing arrangements. ASU 2016-02 is effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted. A modified retrospective approach is required. The Company has formed a project team to evaluate the impact that the adoption of this standard will have on its consolidated financial statements and disclosures. The project team has completed training on the new standard and has started lease review and documentation, but the Company has not yet determined the effect of ASU 2016-02 on its ongoing financial reporting. In November 2015, the FASB issued ASU 2015-17, “Balance Sheet Classification of Deferred Taxes” (“ASU 2015-17”) which requires that deferred tax liabilities and assets be classified as noncurrent on the balance sheet. The current requirement that deferred tax liabilities and assets of a tax-paying component of an entity be offset and presented as a single amount is not affected by this guidance. The guidance may be applied either prospectively to all deferred tax liabilities and assets or retrospectively to all periods presented. The Company adopted the provisions of ASU 2015-17 on January 1, 2017 on a retrospective basis. The December 31, 2016 current deferred tax assets of $13,604,000 have been reclassified in the consolidated balance sheet from current deferred income taxes asset to noncurrent deferred income taxes liability. In July 2015, the FASB issued ASU 2015-11, “Inventory (Topic 330): Simplifying the Measurement of Inventory” (“ASU 2015-11”) which applies to inventory that is measured using first-in, first-out (“FIFO”) or average cost. Under the guidance, an entity should measure inventory that is within the scope of this update at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal and transportation. ASU 2015-11 is effective for annual and interim periods beginning after December 15, 2016, and should be applied prospectively with early adoption permitted at the beginning of an interim period or annual reporting period. The Company adopted the provisions of ASU 2015-11 on January 1, 2017 and, based on a lower of cost and net realizable value inventory analysis as of December 31, 2016, no adjustments to inventory value were required. The analysis reflected the inventory values are proper within the guidance of ASU 2015-11. In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers” (“ASU 2014-09”). ASU 2014-09 requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 will replace most existing revenue recognition guidance in United States Generally Accepted Accounting Principles when it becomes effective. In July 2015, the FASB voted to delay the effective date of ASU 2014-09 by one year, making it effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, with early adoption permitted as of the original effective date. ASU 2014-09 permits the use of either the retrospective, modified retrospective or prospective with a cumulative catch-up approach. The Company will adopt ASU 2014-09 on January 1, 2018 with a cumulative adjustment that will decrease retained earnings by approximately $10,000,000 rather than restating previously reported results. The cumulative adjustment will primarily relate to recognition of revenue on certain contract manufacturing activities, primarily construction of new pressure pumping units in the Company’s distribution and services segment. The Company currently recognizes revenue on manufacturing and assembly projects on a percentage of completion method using measurements of progress towards completion appropriate for the work performed. Upon the adoption of ASU 2014-09, the Company will recognize the revenues on contract manufacturing activities upon shipment and transfer of control versus the percentage of completion method.

Acquisitions (Tables)

12 Months Ended

Dec. 31, 2017

Acquisitions [Abstract]

Consideration Transferred

Total consideration transferred was as follows (in thousands):

Cash consideration paid	$	377,967
Stock consideration through issuance of Company common stock		366,554
Fair value of consideration transferred	$	744,521

Fair Values of Assets Acquired and Liabilities Assumed

The fair values of the assets acquired and liabilities assumed recorded at the acquisition date were as follows (in thousands):

Assets:
Cash	$	98
Accounts receivable		97,891
Inventories		150,000
Prepaid expenses and other current assets		3,850
Property and equipment		141,885
Goodwill		331,728
Other assets		158,130
Total assets	$	883,582


Liabilities:
Current portion of long-term debt	$	1,501
Bank notes payable		1,589
Income taxes payable		850
Accounts payable		72,200
Accrued liabilities		31,803
Deferred revenues		18,806
Long-term debt		10,634
Other long-term liabilities		1,678
Total liabilities	$	139,061
Net assets acquired	$	744,521

Inventories (Tables)

12 Months Ended

Dec. 31, 2017

Inventories [Abstract]

Schedule of Details of Inventories

The following table presents the details of inventories as of December 31, 2017 and 2016 (in thousands):

	December 31, 2017		December 31, 2016
Finished goods	$	242,333	$	178,740
Work in process		73,396		6,662
	$	315,729	$	185,402

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2017

Long-Term Debt [Abstract]

Schedule of Long-Term Debt

Long-term debt at December 31, 2017 and 2016 consisted of the following (in thousands):

	2017			2016
Long-term debt, including current portion:
$850,000,000 revolving credit facility due June 26, 2022	$	495,845		$	225,986
$150,000,000 senior notes Series A due February 27, 2020		150,000			150,000
$350,000,000 senior notes Series B due February 27, 2023		350,000			350,000
$10,000,000 credit line due June 30, 2019		—			—
Bank notes payable		3			—
		995,848			725,986
Unamortized debt issuance costs		(3,442	)		(3,184	)
	$	992,406		$	722,802

Schedule of Aggregate Payments due on the Long-Term Debt

The aggregate payments due on the long-term debt in each of the next five years were as follows (in thousands):

2018	$	3
2019		—
2020		150,000
2021		—
2022		495,845
Thereafter		350,000
	$	995,848

Taxes on Income (Tables)

12 Months Ended

Dec. 31, 2017

Taxes on Income [Abstract]

Earnings Before Taxes

Earnings before taxes on income and details of the provision for taxes on income for the years ended December 31, 2017, 2016 and 2015 were as follows (in thousands):

	2017			2016		2015
Earnings (loss) before taxes on income:
United States	$	74,267		$	227,746	$	361,712
Foreign		(1,253	)		—		—
	$	73,014		$	227,746	$	361,712

Provision (benefit) for taxes on income:
U.S. Federal:
Current	$	11,143		$	28,919	$	64,707
Deferred		(258,703	)		49,685		59,582
	$	(247,560	)	$	78,604	$	124,289
U.S. State:
Current	$	3,861		$	4,727	$	6,280
Deferred		2,280			1,611		3,173
	$	6,141		$	6,338	$	9,453
Foreign:
Current	$	370		$	—	$	—
Deferred		160			—		—
	$	530		$	—	$	—
Consolidated:
Current	$	15,374		$	33,646	$	70,987
Deferred		(256,263	)		51,296		62,755
	$	(240,889	)	$	84,942	$	133,742

Schedule of Effective Income Tax Rate Reconciliation

The Company’s provision for taxes on income varied from the statutory federal income tax rate for the years ended December 31, 2017, 2016 and 2015 due to the following:

	2017			2016			2015
United States income tax statutory rate		35.0	%		35.0	%		35.0	%
State and local taxes, net of federal benefit		0.9			1.8			1.7
Change due to U.S. tax reform		(369.0	)		—			—
Other – net		3.2			0.5			0.3
		(329.9	)%		37.3	%		37.0	%

Schedule of Deferred Tax Assets and Liabilities

The tax effects of temporary differences that give rise to significant portions of the non-current deferred tax assets and liabilities at December 31, 2017 and 2016 were as follows (in thousands):

	2017			2016
Non-current deferred tax assets and liabilities:
Deferred tax assets:
Compensated absences	$	432		$	739
Allowance for doubtful accounts		1,875			2,534
Postretirement health care benefits		1,190			2,234
Insurance accruals		4,599			9,128
Deferred compensation		1,849			11,124
Unrealized loss on defined benefit plans		11,097			28,832
Operating loss carryforwards		15,540			7,846
Pension benefits		549			—
Other		18,474			25,735
		55,605			88,172
Valuation allowances		(15,308	)		(7,417	)
		40,297			80,755
Deferred tax liabilities:
Property		(428,947	)		(654,751	)
Deferred state taxes		(58,366	)		(54,812	)
Pension benefits		—			(2,799	)
Goodwill and other intangibles		(9,015	)		(51,551	)
Other		(12,420	)		(22,295	)
		(508,748	)		(786,208	)
	$	(468,451	)	$	(705,453	)

Reconciliation of Liability for Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of the liability for unrecognized tax benefits for the years ended December 31, 2017, 2016 and 2015, is as follows (in thousands):

	2017			2016			2015
Balance at beginning of year	$	2,019		$	1,958		$	1,171
Additions based on tax positions related to the current year		403			187			339
Additions for tax positions of prior years		273			867			785
Reductions for tax positions of prior years		(908	)		(441	)		(337	)
Settlements		—			(552	)		—
Balance at end of year	$	1,787		$	2,019		$	1,958

Leases (Tables)

12 Months Ended

Dec. 31, 2017

Leases [Abstract]

Schedule of Rent Expense

Total rental expense for the years ended December 31, 2017, 2016 and 2015 was as follows (in thousands):

	2017		2016		2015
Rental expense:
Marine equipment — barges	$	11,550	$	13,791	$	14,092
Marine equipment — towing vessels		116,690		137,609		143,067
Other buildings and equipment		15,915		11,182		9,383
Rental expense	$	144,155	$	162,582	$	166,542

Schedule of Future Minimum Lease Payments under Operating Leases

Future minimum lease payments under operating leases that have initial or remaining noncancelable lease terms in excess of one year at December 31, 2017 were as follows (in thousands):

	Land, Buildings		Marine Equipment
	And Equipment		Barges		Towing Vessels		Total
2018	$	18,888	$	8,711	$	59,185	$	86,784
2019		15,153		4,573		8,727		28,453
2020		12,432		3,806		2,578		18,816
2021		11,384		1,567		2,578		15,529
2022		9,436		1,567		2,578		13,581
Thereafter		73,382		896		12,889		87,167
	$	140,675	$	21,120	$	88,535	$	250,330

Stock Award Plans (Tables)

12 Months Ended

Dec. 31, 2017

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Compensation Cost Breakdown in Statement of Earnings

	2017		2016		2015
Compensation cost	$	11,460	$	11,675	$	11,104
Income tax benefit	$	4,333	$	4,378	$	4,120

Summary of Stock Option Valuation Assumptions

The key input variables used in valuing the stock options during the years ended December 31, 2017, 2016 and 2015 were as follows:

	2017			2016			2015
Dividend yield	None			None			None
Average risk-free interest rate		2.0	%		1.5	%		1.3	%
Stock price volatility		27	%		30	%		33	%
Estimated option term	Six years			Six years			Six years

Employee Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of Stock Option Activity

The following is a summary of the stock option activity under the employee plan described above for the years ended December 31, 2017, 2016 and 2015:

	Outstanding Non- Qualified or Nonincentive Stock Awards			Weighted Average Exercise Price
Outstanding at December 31, 2014		322,956		$	69.95
Granted		114,894		$	74.99
Canceled or expired		(7,418	)	$	86.28
Outstanding at December 31, 2015		430,432		$	71.01
Granted		186,706		$	53.50
Canceled or expired		(16,017	)	$	80.17
Outstanding at December 31, 2016		601,121		$	65.33
Granted		123,141		$	68.46
Exercised		(36,616	)	$	47.95
Canceled or expired		(32,991	)	$	74.07
Outstanding at December 31, 2017		654,655		$	66.45

Summary of Outstanding and Exercisable Stock Options

The following table summarizes information about the Company’s outstanding and exercisable stock options under the employee plan at December 31, 2017:

		Options Outstanding								Options Exercisable
Range of Exercise Prices		Number Outstanding		Weighted Average Remaining Contractual Life in Years		Weighted Average Exercise Price		Aggregated Intrinsic Value		Number Exercisable		Weighted Average Exercise Price		Aggregated Intrinsic Value
$	46.74 – $51.23		197,776		3.8	$	50.02				100,806	$	48.86
$	64.65 – $74.99		394,704		4.0	$	69.68				217,627	$	70.25
$	93.64 – $96.85		33,987		3.1	$	94.31				33,987	$	94.31
$	101.46 – $104.37		28,188		3.2	$	102.88				28,188	$	102.88
$	46.74 – $104.37		654,655		3.8	$	66.45	$	3,455,000		380,608	$	69.15	$	1,883,000

Summary of Restricted Stock Award Activity

The following is a summary of the restricted stock award activity under the employee plan described above for the years ended December 31, 2017, 2016 and 2015:

	Unvested Restricted Stock Award Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested balance at December 31, 2014		321,453		$	71.04
Granted		122,740		$	75.04
Vested		(113,958	)	$	60.73
Forfeited		(18,508	)	$	82.00
Nonvested balance at December 31, 2015		311,727		$	75.73
Granted		190,610		$	53.56
Vested		(105,109	)	$	69.93
Forfeited		(19,573	)	$	76.06
Nonvested balance at December 31, 2016		377,655		$	66.14
Granted		127,255		$	68.50
Vested		(105,600	)	$	68.91
Forfeited		(35,189	)	$	69.45
Nonvested balance at December 31, 2017		364,121		$	65.84

Director Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of Stock Option Activity

The following is a summary of the stock option activity under the director plan described above for the years ended December 31, 2017, 2016, and 2015:

	Outstanding Non- Qualified or Nonincentive Stock Awards			Weighted Average Exercise Price
Outstanding at December 31, 2014		298,334		$	60.01
Exercised		(77,905	)	$	47.65
Outstanding at December 31, 2015		220,429		$	64.37
Exercised		(9,000	)	$	35.72
Canceled or expired		(6,000	)	$	99.52
Outstanding at December 31, 2016		205,429		$	64.60
Granted		3,188		$	70.65
Exercised		(39,000	)	$	46.23
Canceled or expired		(12,000	)	$	87.35
Outstanding at December 31, 2017		157,617		$	67.54

Summary of Outstanding and Exercisable Stock Options

The following table summarizes information about the Company’s outstanding and exercisable stock options under the director plan at December 31, 2017:

		Options Outstanding								Options Exercisable
Range of Exercise Prices		Number Outstanding		Weighted Average Remaining Contractual Life in Years		Weighted Average Exercise Price		Aggregate Intrinsic Value		Number Exercisable		Weighted Average Exercise Price		Aggregate Intrinsic Value
$	29.60		6,000		1.3	$	29.60				6,000	$	29.60
$	41.24 – $56.45		53,276		2.4	$	52.77				53,276	$	52.77
$	61.89 – $62.48		35,153		4.5	$	62.31				35,153	$	62.31
$	70.65 – $99.52		63,188		6.0	$	86.50				62,391	$	86.71
$	29.60 – $99.52		157,617		4.3	$	67.54	$	1,128,000		156,820	$	67.52	$	1,128,000

Summary of Restricted Stock Award Activity

The following is a summary of the restricted stock award activity under the director plan described above for the years ended December 31, 2017, 2016 and 2015:

	Unvested Restricted Stock Award Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested balance at December 31, 2014		292		$	99.52
Granted		20,350		$	78.52
Vested		(18,851	)	$	79.77
Nonvested balance at December 31, 2015		1,791		$	68.73
Granted		23,074		$	64.89
Vested		(24,518	)	$	65.17
Nonvested balance at December 31, 2016		347		$	64.89
Granted		21,198		$	70.65
Vested		(21,226	)	$	70.56
Nonvested balance at December 31, 2017		319		$	70.65

Retirement Plans (Tables)

12 Months Ended

Dec. 31, 2017

Defined Benefit Plan Disclosure [Line Items]

Summary of Asset Allocation

As of December 31, 2017 and 2016, these assets were allocated among asset categories as follows:

Asset Category	2017			2016			Current Minimum, Target and Maximum Allocation Policy
U.S. equity securities		51	%		51	%		30% — 50%— 70	%
International equity securities		21	%		19	%		0% — 20%— 30	%
Debt securities		28	%		30	%		15% — 30%— 55	%
Cash and cash equivalents		—	%		—	%		0% — 0%— 5	%
		100	%		100	%

Schedule of Change in Benefit Obligation

The following table presents the change in benefit obligation and plan assets for the Company’s defined benefit plans and postretirement benefit plan (in thousands):

															Other Postretirement Benefits
	Pension Benefits														Postretirement
	Pension Plan								SERP						Welfare Plan
	2017				2016				2017			2016			2017			2016
Change in benefit obligation
Benefit obligation at beginning of year		$	337,176			$	297,325		$	1,457		$	1,526		$	675		$	891
Service cost			10,677				13,402			—			—			—			—
Interest cost			13,729				14,123			58			65			27			29
Actuarial loss (gain)			34,563				19,120			42			12			52			(198	)
Curtailments			(33,433	)			—			—			—			—			—
Gross benefits paid			(7,718	)			(6,794	)		(145	)		(146	)		(75	)		(47	)
Benefit obligation at end of year		$	354,994			$	337,176		$	1,412		$	1,457		$	679		$	675

Accumulated benefit obligation at end of year		$	324,904			$	272,591		$	1,412		$	1,457		$	679		$	675

Weighted-Average Assumption Used to Determine Benefit Obligation and Net Periodic Benefit Cost

Weighted-average assumption used to determine benefit obligation at end of year
Discount rate		3.7	%		4.2	%	3.7	%	4.2	%	3.7	%	4.2	%
Rate of compensation increase	Service-based table			Service- based table			—		—		—		—
Health care cost trend rate
Initial rate		—			—		—		—		7.0	%	7.0	%
Ultimate rate		—			—		—		—		5.0	%	5.0	%
Years to ultimate		—			—		—		—		2022		2021

Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rate


Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation
Increase	$	—	$	—	$	—	$	—	$	75		$	74
Decrease		—		—		—		—		(65	)		(64	)

Summary of Change in Plan Assets

Change in plan assets
Fair value of plan assets at beginning of year	$	257,517		$	243,588		$	—		$	—		$	—		$	—
Actual return on plan assets		45,196			20,723			—			—			—			—
Employer contribution		—			—			145			146			75			47
Gross benefits paid		(7,718	)		(6,794	)		(145	)		(146	)		(75	)		(47	)
Fair value of plan assets at end of year	$	294,995		$	257,517		$	—		$	—		$	—		$	—

Summary of Funded Status at End of Year

													Other Postretirement Benefits
	Pension Benefits												Postretirement Welfare Plan
	Pension Plan						SERP						Postretirement Welfare Plan
	2017			2016			2017			2016			2017			2016
Funded status at end of year
Fair value of plan assets	$	294,995		$	257,517		$	—		$	—		$	—		$	—
Benefit obligations		(354,994	)		(337,176	)		(1,412	)		(1,457	)		(679	)		(675	)
Funded status and amount recognized at end of year	$	(59,999	)	$	(79,659	)	$	(1,412	)	$	(1,457	)	$	(679	)	$	(675	)

Amounts Recognized in the Consolidated Balance Sheets

Amounts recognized in the consolidated balance sheets
Noncurrent asset	$	—		$	—		$	—		$	—		$	—		$	—
Current liability		—			—			(159	)		(150	)		(54	)		(56	)
Long-term liability		(59,999	)		(79,659	)		(1,253	)		(1,307	)		(625	)		(619	)

Amounts Recognized in Accumulated Other Comprehensive Income

Amounts recognized in accumulated other comprehensive income
Net actuarial loss (gain)	$	57,387	$	87,658	$	508	$	494	$	(5,053	)	$	(5,773	)
Prior service cost (credit)		—		—		—		—		—			—
Accumulated other compensation income	$	57,387	$	87,658	$	508	$	494	$	(5,053	)	$	(5,773	)

Projected Benefit Obligation in Excess of Plan Assets

	Pension Benefits
	Pension Plan				SERP
	2017		2016		2017		2016
Projected benefit obligation in excess of plan assets
Projected benefit obligation at end of year	$	354,994	$	337,176	$	1,412	$	1,457
Fair value of plan assets at end of year		294,995		257,517		—		—

Accumulated Benefit Obligation in Excess of Plan Assets

	Pension Benefits
	Pension Plan				SERP
	2017		2016		2017		2016
Accumulated benefit obligation in excess of plan assets
Projected benefit obligation at end of year	$	354,994	$	337,176	$	1,412	$	1,457
Accumulated benefit obligation at end of year		324,904		272,591		1,412		1,457
Fair value of plan assets at end of year		294,995		257,517		—		—

Schedule of Employer Contribution

The following tables presents the expected cash flows for the Company’s defined benefit plans and postretirement benefit plan at December 31, 2017 and 2016 (in thousands):

									Other Postretirement Benefits
	Pension Benefits								Postretirement
	Pension Plan				SERP				Welfare Plan
	2017		2016		2017		2016		2017		2016
Expected employer contributions
First year	$	—	$	—	$	162	$	153	$	48	$	50

Expected Benefit Payments

									Other Postretirement Benefits
	Pension Benefits								Postretirement
	Pension Plan				SERP				Welfare Plan
	2017		2016		2017		2016		2017		2016
Expected benefit payments (gross)
Year one	$	9,483	$	8,032	$	162	$	153	$	55	$	58
Year two		10,131		8,835		159		157		56		58
Year three		10,818		9,646		156		155		58		58
Year four		11,608		10,400		152		151		58		58
Year five		12,377		11,201		149		148		46		57
Next five years		75,717		70,419		462		514		214		199

Summary of Expected Federal Subsidy

									Other Postretirement Benefits
	Pension Benefits								Postretirement
	Pension Plan				SERP				Welfare Plan
	2017		2016		2017		2016		2017			2016
Expected federal subsidy
Year one	$	—	$	—	$	—	$	—	$	(7	)	$	(7	)
Year two		—		—		—		—		(6	)		(7	)
Year three		—		—		—		—		(6	)		(7	)
Year four		—		—		—		—		(6	)		(7	)
Year five		—		—		—		—		(7	)		(7	)
Next five years		—		—		—		—		(30	)		(33	)

Pension Benefits [Member]

Defined Benefit Plan Disclosure [Line Items]

Components of Net Periodic Benefit Cost

	Pension Benefits
	Pension Plan									SERP
	2017			2016			2015			2017		2016		2015
Components of net periodic benefit cost
Service cost	$	10,677		$	13,402		$	14,683		$	—	$	—	$	—
Interest cost		13,729			14,123			13,302			58		65		64
Expected return on plan assets		(18,195	)		(16,805	)		(17,921	)		—		—		—
Amortization:
Actuarial loss		4,400			5,484			7,728			28		26		28
Prior service credit		—			—			—			—		—		—
Net periodic benefit cost		10,611			16,204			17,792			86		91		92

Other changes in plan assets and benefit obligations recognized in other comprehensive income
Current year actuarial loss (gain)		7,562			15,203			(19,127	)		42			12			(30	)
Recognition of actuarial loss		(37,833	)		(5,484	)		(7,728	)		(28	)		(26	)		(28	)
Recognition of prior service credit		—			—			—			—			—			—
Total recognized in other comprehensive income		(30,271	)		9,719			(26,855	)		14			(14	)		(58	)

Total recognized in net periodic benefit cost and other comprehensive income	$	(19,660	)	$	25,923		$	(9,063	)	$	100		$	77		$	34

Weighted-Average Assumption Used to Determine Benefit Obligation and Net Periodic Benefit Cost

Weighted average assumptions used to determine net periodic benefit cost
Discount rate (1)		4.2/4.0	%		4.5	%	4.1	%	4.2	%	4.5	%	4.1	%
Expected long-term rate of return on plan assets		7.0	%		7.0	%	7.5	%	—		—		—
Rate of compensation increase	Service- based table			Service- based table			4.25	%	—		—		—

Estimated Amounts that will be Amortized from Accumulated Other Comprehensive Income into Net Periodic Benefit Cost

The estimated amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2018 are as follows (in thousands):

	Pension Benefits
	Pension Plan		SERP
Actuarial loss	$	2,820	$	23
Prior service credit		—		—
	$	2,820	$	23

Other Postretirement Benefits [Member]

Defined Benefit Plan Disclosure [Line Items]

Components of Net Periodic Benefit Cost

	Other Postretirement Benefits
	Postretirement Welfare Plan
	2017			2016			2015
Components of net periodic benefit cost
Service cost	$	—		$	—		$	—
Interest cost		27			29			36
Amortization:
Actuarial gain		(668	)		(747	)		(793	)
Prior service cost		—			—			—
Net periodic benefit cost		(641	)		(718	)		(757	)

Other changes in benefit obligations recognized in other comprehensive income
Current year actuarial gain		52		(198	)		(322	)
Recognition of actuarial gain		668		747			793
Recognition of prior service cost		—		—			—
Adjustment for actual Medicare Part D reimbursement		—		(3	)		(3	)
Total recognized in other comprehensive income		720		546			468

Total recognized in net periodic benefit cost and other comprehensive income	$	79	$	(172	)	$	(289	)

Weighted-Average Assumption Used to Determine Benefit Obligation and Net Periodic Benefit Cost

Weighted average assumptions used to determine net periodic benefit cost
Discount rate	4.2	%	4.5	%	4.1	%
Health care cost trend rate:
Initial rate	7.0	%	6.5	%	7.0	%
Ultimate rate	5.0	%	5.0	%	5.0	%
Years to ultimate	2021		2019		2019

Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rate

Effect of one-percentage-point change in assumed health care cost trend rate on aggregate service and interest cost
Increase	$	3		$	4		$	5
Decrease		(3	)		(3	)		(4	)

Estimated Amounts that will be Amortized from Accumulated Other Comprehensive Income into Net Periodic Benefit Cost

The estimated amounts that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2018 are as follows (in thousands):

	Other Postretirement Benefits
	Postretirement Welfare Plan
Actuarial gain	$	(596	)
Prior service cost		—
	$	(596	)

Other Comprehensive Income (Tables)

12 Months Ended

Dec. 31, 2017

Other Comprehensive Income [Abstract]

Schedule of Changes in Other Comprehensive income

The Company’s changes in other comprehensive income for the years ended December 31, 2017, 2016 and 2015 were as follows (in thousands):

	2017									2016									2015
	Gross Amount			Income Tax (Provision) Benefit			Net Amount			Gross Amount			Income Tax (Provision) Benefit			Net Amount			Gross Amount		Income Tax (Provision) Benefit			Net Amount
Pension and postretirement benefits (a):
Amortization of net actuarial loss	$	3,760		$	(1,417	)	$	2,343		$	4,763		$	(1,825	)	$	2,938		$	6,963	$	(2,667	)	$	4,296
Actuarial gains (losses)		25,776			(9,371	)		16,405			(15,013	)		5,754			(9,259	)		19,482		(7,456	)		12,026

Foreign currency translation adjustments		(146	)		—			(146	)		—			—			—			29		—			29

Total	$	29,390		$	(10,788	)	$	18,602		$	(10,250	)	$	3,929		$	(6,321	)	$	26,474	$	(10,123	)	$	16,351

(a)	Actuarial gains (losses) are amortized into costs of sales and operating expenses or selling, general and administrative expenses as appropriate. (See Note 10 – Retirement Plans)

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Earnings Per Share

The following table presents the components of basic and diluted earnings per share for the years ended December 31, 2017, 2016 and 2015 (in thousands, except per share amounts):

	2017			2016			2015
Net earnings attributable to Kirby	$	313,187		$	141,406		$	226,684
Undistributed earnings allocated to restricted shares		(2,213	)		(999	)		(1,345	)
Income available to Kirby common stockholders — basic		310,974			140,407			225,339
Undistributed earnings allocated to restricted shares		2,213			999			1,345
Undistributed earnings reallocated to restricted shares		(2,211	)		(997	)		(1,343	)
Income available to Kirby common stockholders — diluted	$	310,976		$	140,409		$	225,341

Shares outstanding:
Weighted average common stock issued and outstanding		55,702			53,834			55,056
Weighted average unvested restricted stock		(394	)		(380	)		(327	)
Weighted average common stock outstanding — basic		55,308			53,454			54,729
Dilutive effect of stock options		53			58			97
Weighted average common stock outstanding — diluted		55,361			53,512			54,826
Net earnings per share attributable to Kirby common stockholders:
Basic	$	5.62		$	2.63		$	4.12

Diluted	$	5.62		$	2.62		$	4.11

Quarterly Results (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Results (Unaudited) [Abstract]

Schedule of Quarterly Results

The unaudited quarterly results for the year ended December 31, 2017 were as follows (in thousands, except per share amounts):

	Three Months Ended
	March 31, 2017			June 30, 2017			September 30, 2017			December 31, 2017
Revenues	$	491,705		$	473,328		$	541,274		$	708,111
Costs and expenses		446,233			425,708			487,753			755,990
Gain (loss) on disposition of assets		99			(139	)		(159	)		(4,288	)
Operating income (loss)		45,571			47,481			53,362			(52,167	)
Other income (expense)		(116	)		(1	)		(113	)		469
Interest expense		(4,457	)		(4,465	)		(5,388	)		(7,162	)
Earnings before taxes on income		40,998			43,015			47,861			(58,860	)
Benefit (provision) for taxes on income		(13,353	)		(17,043	)		(19,072	)		290,357
Net earnings		27,645			25,972			28,789			231,497
Less: Net earnings attributable to noncontrolling interests		(162	)		(194	)		(182	)		(178	)
Net earnings attributable to Kirby	$	27,483		$	25,778		$	28,607		$	231,319

Net earnings per share attributable to Kirby common stockholders:
Basic	$	0.51		$	0.48		$	0.52		$	3.88
Diluted	$	0.51		$	0.48		$	0.52		$	3.87

The unaudited quarterly results for the year ended December 31, 2016 were as follows (in thousands, except per share amounts):

	Three Months Ended
	March 31, 2016			June 30, 2016			September 30, 2016			December 31, 2016
Revenues	$	458,733		$	441,582		$	434,708		$	435,650
Costs and expenses		393,399			374,868			378,400			378,684
Gain (loss) on disposition of assets		67			94			(122	)		(166	)
Operating income		65,401			66,808			56,186			56,800
Other income (expense)		135			179			(120	)		47
Interest expense		(4,193	)		(4,513	)		(4,507	)		(4,477	)
Earnings before taxes on income		61,343			62,474			51,559			52,370
Provision for taxes on income		(22,859	)		(23,365	)		(19,206	)		(19,512	)
Net earnings		38,484			39,109			32,353			32,858
Less: Net earnings attributable to noncontrolling interests		(385	)		(167	)		(343	)		(503	)
Net earnings attributable to Kirby	$	38,099		$	38,942		$	32,010		$	32,355

Net earnings per share attributable to Kirby common stockholders:
Basic	$	0.71		$	0.72		$	0.59		$	0.60
Diluted	$	0.71		$	0.72		$	0.59		$	0.60

Segment Data (Tables)

12 Months Ended

Dec. 31, 2017

Segment Data [Abstract]

Schedule of Segment Reporting Information, by Segment

	2017			2016			2015
Revenues:
Marine transportation	$	1,324,106		$	1,471,893		$	1,663,090
Distribution and services		890,312			298,780			484,442
	$	2,214,418		$	1,770,673		$	2,147,532
Segment profit (loss):
Marine transportation	$	136,011		$	257,102		$	374,842
Distribution and services		86,585			3,186			18,921
Other		(149,582	)		(32,542	)		(32,051	)
	$	73,014		$	227,746		$	361,712
Total assets:
Marine transportation	$	3,485,099		$	3,613,951		$	3,444,785
Distribution and services		1,567,085			623,268			632,764
Other		75,243			52,676			63,009
	$	5,127,427		$	4,289,895		$	4,140,558
Depreciation and amortization:
Marine transportation	$	178,898		$	184,291		$	175,798
Distribution and services		20,387			12,833			12,498
Other		3,596			3,793			3,944
	$	202,881		$	200,917		$	192,240
Capital expenditures:
Marine transportation	$	165,421		$	217,423		$	311,862
Distribution and services		5,086			5,915			28,907
Other		6,715			7,728			4,706
	$	177,222		$	231,066		$	345,475

Schedule of Other Segment Reporting Information

The following table presents the details of “Other” segment profit (loss) for the years ended December 31, 2017, 2016 and 2015 (in thousands):

	2017			2016			2015
General corporate expenses	$	(18,150	)	$	(14,966	)	$	(14,773	)
Interest expense		(21,472	)		(17,690	)		(18,738	)
Impairment of long-lived assets		(105,712	)		—			—
Gain (loss) on disposition of assets		(4,487	)		(127	)		1,672
Other income (expense)		239			241			(212	)
	$	(149,582	)	$	(32,542	)	$	(32,051	)

The following table presents the details of “Other” total assets as of December 31, 2017, 2016 and 2015 (in thousands):

	2017		2016		2015
General corporate assets	$	73,353	$	50,054	$	60,919
Investment in affiliates		1,890		2,622		2,090
	$	75,243	$	52,676	$	63,009

Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts Receivable [Abstract]
Accruals for revenues earned included in accounts receivable	$ 153,661,000	$ 84,453,000
Receivables from insurance companies to cover claims in excess included in accounts receivable	$ 66,588,000	88,182,000
Drydocking on Ocean-Going Vessels [Abstract]
Period in which recertification of ocean going vessels occur twice	5 years
Recognized amortization of major maintenance costs	$ 21,207,000	19,869,000	$ 22,126,000
Capitalized interest excluded from interest expense	1,731,000	2,974,000	3,026,000
Goodwill [Abstract]
Impairment of goodwill	0	0
Gross carrying value of goodwill	947,502,000	615,598,000
Accumulated amortization	15,566,000	15,566,000
Accumulated impairment losses	1,901,000	1,901,000
Net goodwill	935,135,000	598,131,000
Other Intangibles [Abstract]
Intangible assets gross carrying amounts	315,983,000	158,634,000
Intangible assets accumulated amortization	83,175,000	71,328,000
Intangible assets net carrying amount	232,808,000	87,306,000
Intangible liabilities gross carrying value	7,437,000	5,759,000
Intangible liabilities accumulated amortization	4,751,000	3,949,000
Intangible liabilities net carrying amount	2,686,000	1,810,000
Amortization of intangible assets	11,296,000	8,467,000	8,526,000
Intangible Assets and liabilities, Estimated Amortization Expense, Fiscal Year Maturity [Abstract]
2018	17,760,000
2019	17,395,000
2020	17,617,000
2021	17,171,000
2022	$ 16,971,000
Weighted average amortization period for intangible assets and liabilities	15 years
Accrued Insurance [Abstract]
Accrued insurance liabilities	$ 26,195,000	23,085,000	23,737,000
Minimum [Member]
Drydocking on Ocean-Going Vessels [Abstract]
Period of amortization of shipyard costs	30 months
Maximum [Member]
Drydocking on Ocean-Going Vessels [Abstract]
Period of amortization of shipyard costs	60 months
Marine Transportation Equipment [Member] \| Minimum [Member]
Property, Maintenance and Repairs [Abstract]
Estimated useful lives of the individual assets	5 years
Marine Transportation Equipment [Member] \| Maximum [Member]
Property, Maintenance and Repairs [Abstract]
Estimated useful lives of the individual assets	40 years
Buildings [Member] \| Minimum [Member]
Property, Maintenance and Repairs [Abstract]
Estimated useful lives of the individual assets	10 years
Buildings [Member] \| Maximum [Member]
Property, Maintenance and Repairs [Abstract]
Estimated useful lives of the individual assets	40 years
Other Equipment [Member] \| Minimum [Member]
Property, Maintenance and Repairs [Abstract]
Estimated useful lives of the individual assets	2 years
Other Equipment [Member] \| Maximum [Member]
Property, Maintenance and Repairs [Abstract]
Estimated useful lives of the individual assets	10 years
Marine Transportation Segment [Member]
Goodwill [Abstract]
Net goodwill	$ 387,504,000	382,227,000
Marine Transportation Segment [Member] \| Minimum [Member]
Revenue Recognition [Abstract]
Range of term contracts	1 year
Marine Transportation Segment [Member] \| Maximum [Member]
Revenue Recognition [Abstract]
Range of term contracts	5 years
Distribution and Services Segment [Member]
Goodwill [Abstract]
Net goodwill	$ 547,631,000	215,904,000
ASU 2016-09 [Member]
Accounting Standards [Abstract]
Cumulative effect on retained earnings		(8,486,000)
Effect of change on operating activities and financing activities		1,756,000	$ 2,975,000
ASU 2015-17 [Member]
Accounting Standards [Abstract]
Reclassification of deferred income taxes		$ 13,604,000
ASU 2014-09 [Member]
Accounting Standards [Abstract]
Cumulative effect on retained earnings	$ (10,000,000)

Acquisitions (Details) $ / shares in Units, $ in Thousands								1 Months Ended	12 Months Ended
Acquisitions (Details) $ / shares in Units, $ in Thousands	Oct. 20, 2017 USD ($)	Sep. 13, 2017 USD ($) Branch State $ / shares shares	Jul. 10, 2017 USD ($) Vessel bbl hp	Oct. 11, 2016 USD ($) State	Jun. 30, 2016 USD ($) Vessel bbl	Jun. 02, 2016 USD ($) Vessel	Apr. 15, 2016 USD ($) Vessel bbl	Jul. 31, 2017 USD ($) Vessel	Dec. 31, 2017 USD ($)	Jun. 26, 2017 USD ($)	Jun. 25, 2017 USD ($)	Dec. 31, 2016 USD ($)
Assets [Abstract]
Goodwill									$ 935,135			$ 598,131
Sneed Shipbuilding, Inc [Member]
Total consideration transferred [Abstract]
Cash consideration paid	$ 14,852
Stewart & Stevenson LLC [Member]
Business Acquisition [Line Items]
Purchase price before post-closing adjustment and transaction fees		$ 758,245
Assumption of debt		$ 13,724
Issuance of shares (in shares) \| shares		5,696,259
Price per share (in dollars per share) \| $ / shares		$ 64.35
Term debt assumed		$ 12,135
Number of branches \| Branch		42
Number of states having branches \| State		12
Intangible assets acquired		$ 155,722
Weighted average amortization period of intangibles									16 years 9 months 18 days
Acquisition related costs		21,190
Total consideration transferred [Abstract]
Cash consideration paid		377,967
Stock consideration through issuance of Company common stock		366,554
Fair value of consideration transferred		744,521
Assets [Abstract]
Cash		98
Accounts receivable		97,891
Inventories		150,000
Prepaid expenses and other current assets		3,850
Property and equipment		141,885
Goodwill		331,728
Other assets		158,130
Total assets		883,582
Liabilities [Abstract]
Current portion of long-term debt		1,501
Bank notes payable		1,589
Income taxes payable		850
Accounts payable		72,200
Accrued liabilities		31,803
Deferred revenues		18,806
Long-term debt		10,634
Other long-term liabilities		1,678
Total liabilities		139,061
Net assets acquired		$ 744,521
Stewart & Stevenson LLC [Member] \| Revolving Credit Facility [Member]
Business Acquisition [Line Items]
Maximum borrowing capacity										$ 850,000	$ 550,000
Maturity date									Jun. 26, 2022
Undisclosed Competitor [Member]
Business Acquisition [Line Items]
Intangible assets acquired			$ 30
Weighted average amortization period of intangibles									2 years
Total consideration transferred [Abstract]
Cash consideration paid			68,000
Assets [Abstract]
Property and equipment			$ 67,970
Undisclosed Competitor [Member] \| Pressure Tank Barges [Member]
Business Acquisition [Line Items]
Number of maritime vessels acquired \| Vessel			9
Undisclosed Competitor [Member] \| Barrel Tank Barges [Member]
Business Acquisition [Line Items]
Number of maritime vessels acquired \| Vessel			4
Tank barge barrel capacity \| bbl			30,000
Undisclosed Competitor [Member] \| Inland Tank Barges [Member]
Business Acquisition [Line Items]
Number of maritime vessels acquired \| Vessel			13
Average age of property									5 years
Undisclosed Competitor [Member] \| Inland Towboats [Member]
Business Acquisition [Line Items]
Number of maritime vessels acquired \| Vessel			3
Horsepower of inland towboats \| hp			1,320
Valley Power Systems Northwest, Inc. [Member]
Business Acquisition [Line Items]
Intangible assets acquired				$ 2,070
Weighted average amortization period of intangibles									15 years
Number of western states included in distributor agreement \| State				9
Total consideration transferred [Abstract]
Fair value of consideration transferred				$ 11,440
Assets [Abstract]
Goodwill				$ 8,330
Barge Fleeting and Marine Fueling Operation Business [Member]
Total consideration transferred [Abstract]
Fair value of consideration transferred								$ 3,900
Barge Fleeting and Marine Fueling Operation Business [Member] \| Inland Tank Barges [Member]
Business Acquisition [Line Items]
Number of maritime vessels acquired \| Vessel								4
Total consideration transferred [Abstract]
Fair value of consideration transferred								$ 1,450
TD Equipment Finance, Inc. [Member]
Total consideration transferred [Abstract]
Cash consideration paid					$ 13,682
TD Equipment Finance, Inc. [Member] \| Coastal Tank Barge [Member]
Business Acquisition [Line Items]
Number of maritime vessels acquired \| Vessel					1
Tank barge barrel capacity \| bbl					80,000
Crosby Marine Transportation LLC [Member]
Total consideration transferred [Abstract]
Cash consideration paid						$ 26,450
Crosby Marine Transportation LLC [Member] \| Coastal Tugboats [Member]
Business Acquisition [Line Items]
Number of maritime vessels acquired \| Vessel						4
Average age of property									13 years
SEACOR Holdings Inc. [Member]
Business Acquisition [Line Items]
Ownership transferred, value							$ 3,681
Intangible assets acquired							0
Total consideration transferred [Abstract]
Cash consideration paid							85,500
Fair value of consideration transferred							89,181
Assets [Abstract]
Goodwill							$ 985
SEACOR Holdings Inc. [Member] \| Inland Tank Barges [Member]
Business Acquisition [Line Items]
Number of maritime vessels acquired \| Vessel							27
Tank barge barrel capacity \| bbl							30,000
Average age of property									10 years
SEACOR Holdings Inc. [Member] \| Inland Towboats [Member]
Business Acquisition [Line Items]
Number of maritime vessels acquired \| Vessel							14

Impairment of Long-lived Assets (Details) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2017 USD ($) Tugboat Towboat TankBarge	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Impairment Effects on Earnings Per Share [Line Items]
Non-cash pre-tax impairment charge	$ 105,712	$ 105,712	$ 0	$ 0
Impairment charge after tax effect	$ 66,975
Impairment charge after tax effect on earning per share (in dollars per share) \| $ / shares	$ 1.20
Vessels [Member]
Impairment Effects on Earnings Per Share [Line Items]
Fair market value of assets	$ 12,550	$ 12,550
Coastal Tank Barge [Member]
Impairment Effects on Earnings Per Share [Line Items]
Number of vessels to be disposed of \| TankBarge		12
Coastal Tugboats [Member]
Impairment Effects on Earnings Per Share [Line Items]
Number of vessels to be disposed of \| Tugboat		21
Inland Towboats [Member]
Impairment Effects on Earnings Per Share [Line Items]
Number of vessels to be disposed of \| Towboat		6

Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Details of inventories [Abstract]
Finished goods	$ 242,333	$ 178,740
Work in process	73,396	6,662
Inventory, Net, Total	$ 315,729	$ 185,402

Long-Term Debt, Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Jun. 25, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term Debt	$ 995,848		$ 725,986
Unamortized debt issuance costs	(3,442)		(3,184)
Total	992,406		722,802
Bank Notes Payable [Member]
Debt Instrument [Line Items]
Long-term Debt	3		0
Revolving Credit Facility Due June 26, 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 495,845		225,986
Credit facility, expiration date	Jun. 26, 2022
Long term debt, face amount	$ 850,000
Senior Notes Series A Due February 27, 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 150,000		150,000
Credit facility, expiration date	Feb. 27, 2020
Long term debt, face amount	$ 150,000
Senior Notes Series B Due February 27, 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 350,000		350,000
Credit facility, expiration date	Feb. 27, 2023
Long term debt, face amount	$ 350,000
Credit Line Due June 30, 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt	$ 0		$ 0
Credit facility, expiration date	Jun. 30, 2019
Long term debt, face amount	$ 10,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long term debt, face amount		$ 550,000

Long-Term Debt, Schedule of Aggregate Payments Due on The Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Long-Term Debt [Abstract]
2018	$ 3
2019	0
2020	150,000
2021	0
2022	495,845
Thereafter	350,000
Long-term Debt	$ 995,848	$ 725,986

Long-Term Debt (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2017	Jun. 25, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Line of credit, increase in aggregate commitments	$ 300,000	$ 300,000
Senior Notes	500,000	500,000
Total debt outstanding, Fair value	984,017	984,017		$ 715,330
Short-term debt	3	3
Senior Notes Series A Due February 27, 2020 [Member]
Debt Instrument [Line Items]
Long term debt, face amount	$ 150,000	$ 150,000
Debt instrument, interest rate, stated percentage	2.72%	2.72%
Senior Notes Series B Due February 27, 2023 [Member]
Debt Instrument [Line Items]
Long term debt, face amount	$ 350,000	$ 350,000
Debt instrument, interest rate, stated percentage	3.29%	3.29%
Term Loan Due September 15, 2032 [Member] \| Stewart & Stevenson LLC [Member]
Debt Instrument [Line Items]
Term debt assumed, paid off	$ 12,135
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long term debt, face amount			$ 550,000
Average borrowing under revolving credit facility		$ 270,446
Commitment amount		$ 25,000
Commitment fee		0.10%
Weighted average interest rate	2.20%	2.20%
Revolving Credit Facility [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Interest rate, variable rate basis		LIBOR
Basis spread on variable rate		1.00%
Line Of Credit [Member]
Debt Instrument [Line Items]
Credit facility, amount outstanding	$ 1,117	$ 1,117
Line Of Credit [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, amount outstanding	$ 8,893	$ 8,893

Taxes on Income, Earnings Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Line Items]
Earnings (loss) before taxes on income	$ (58,860)	$ 47,861	$ 43,015	$ 40,998	$ 52,370	$ 51,559	$ 62,474	$ 61,343		$ 73,014	$ 227,746	$ 361,712
U.S. Federal [Abstract]
Current										11,143	28,919	64,707
Deferred										(258,703)	49,685	59,582
Total U.S. Federal										(247,560)	78,604	124,289
U.S. State [Abstract]
Current										3,861	4,727	6,280
Deferred										2,280	1,611	3,173
Total U.S. State										6,141	6,338	9,453
Foreign [Abstract]
Current										370	0	0
Deferred										160	0	0
Total Foreign										530	0	0
Consolidated [Abstract]
Current										15,374	33,646	70,987
Deferred										(256,263)	51,296	62,755
Total Provision (benefit) for taxes on income	$ (290,357)	$ 19,072	$ 17,043	$ 13,353	$ 19,512	$ 19,206	$ 23,365	$ 22,859		$ (240,889)	$ 84,942	$ 133,742
Effective income tax rate										35.00%	35.00%	35.00%
One-time deferred tax benefit										$ (269,472)
Plan [Member]
Consolidated [Abstract]
Effective income tax rate									21.00%
United States [Member]
Income Tax Disclosure [Line Items]
Earnings (loss) before taxes on income										74,267	$ 227,746	$ 361,712
Foreign [Member]
Income Tax Disclosure [Line Items]
Earnings (loss) before taxes on income										$ (1,253)	$ 0	$ 0

Taxes on Income, Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Company's provision for taxes on income varied from the statutory federal income tax rate [Abstract]
United States income tax statutory rate	35.00%	35.00%	35.00%
State and local taxes, net of federal benefit	0.90%	1.80%	1.70%
Change due to U.S. tax reform	(369.00%)	0.00%	0.00%
Other - net	3.20%	0.50%	0.30%
Effective income tax rate	(329.90%)	37.30%	37.00%

Taxes on Income, Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets [Abstract]
Compensated absences	$ 432	$ 739
Allowance for doubtful accounts	1,875	2,534
Postretirement health care benefits	1,190	2,234
Insurance accruals	4,599	9,128
Deferred compensation	1,849	11,124
Unrealized loss on defined benefit plans	11,097	28,832
Operating loss carryforwards	15,540	7,846
Pension benefits	549	0
Other	18,474	25,735
Deferred tax assets, gross	55,605	88,172
Valuation allowances	(15,308)	(7,417)
Deferred tax assets, net of valuation allowance	40,297	80,755
Deferred tax liabilities [Abstract]
Property	(428,947)	(654,751)
Deferred state taxes	(58,366)	(54,812)
Pension benefits	0	(2,799)
Goodwill and other intangibles	(9,015)	(51,551)
Other	(12,420)	(22,295)
Deferred tax liabilities	(508,748)	(786,208)
Net deferred tax liabilities	(468,451)	$ (705,453)
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, net of valuation allowance	$ 232
Expiration dates, operating loss carryforwards	Dec. 31, 2030
Unrecognized tax benefits including interest and penalties	$ 2,462
Amount that would impact the effective tax rate, if recognized	1,947
Canada [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 6,019
Expiration dates, operating loss carryforwards	Dec. 31, 2038
State and Local Jurisdiction [Member] \| Minimum [Member]
Income Tax Examination [Line Items]
Years open to audit under the statute of limitations	2011
State and Local Jurisdiction [Member] \| Maximum [Member]
Income Tax Examination [Line Items]
Years open to audit under the statute of limitations	2016
Internal Revenue Service (IRS) [Member] \| Minimum [Member]
Income Tax Examination [Line Items]
Years open to audit under the statute of limitations	2014
Internal Revenue Service (IRS) [Member] \| Maximum [Member]
Income Tax Examination [Line Items]
Years open to audit under the statute of limitations	2016

Taxes on Income, Reconciliation of Liability for Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the beginning and ending amount of the liability for unrecognized tax benefits [Roll Forward]
Balance at beginning of year	$ 2,019	$ 1,958	$ 1,171
Additions based on tax positions related to the current year	403	187	339
Additions for tax positions of prior years	273	867	785
Reductions for tax positions of prior years	(908)	(441)	(337)
Settlements	0	(552)	0
Balance at end of year	1,787	2,019	1,958
Income tax penalties and interest recognized	120	88	216
Accrued liabilities for payment of interest and penalties	$ 675	$ 554	$ 522

Leases, Schedule of Rent Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Subject To Or Available for Operating Lease [Line Items]
Rental expense	$ 144,155	$ 162,582	$ 166,542
Other Buildings and Equipment [Member]
Property Subject To Or Available for Operating Lease [Line Items]
Rental expense	15,915	11,182	9,383
Barges [Member] \| Marine Equipment [Member]
Property Subject To Or Available for Operating Lease [Line Items]
Rental expense	$ 11,550	13,791	14,092
Towing Vessels [Member]
Property Subject To Or Available for Operating Lease [Line Items]
Percentage of charter agreement for terms of one year or less	75.00%
Towing Vessels [Member] \| Marine Equipment [Member]
Property Subject To Or Available for Operating Lease [Line Items]
Rental expense	$ 116,690	$ 137,609	$ 143,067
Minimum [Member] \| Barges [Member]
Property Subject To Or Available for Operating Lease [Line Items]
Lease agreements expiring terms	1 year
Minimum [Member] \| Towing Vessels [Member]
Property Subject To Or Available for Operating Lease [Line Items]
Lease agreements expiring terms	30 days
Maximum [Member] \| Barges [Member]
Property Subject To Or Available for Operating Lease [Line Items]
Lease agreements expiring terms	12 years
Maximum [Member] \| Towing Vessels [Member]
Property Subject To Or Available for Operating Lease [Line Items]
Lease agreements expiring terms	10 years

Leases, Schedule of Future Minimum Lease Payments Under Operating Leases (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Operating Leased Assets [Line Items]
2018	$ 86,784
2019	28,453
2020	18,816
2021	15,529
2022	13,581
Thereafter	87,167
Future minimum lease payments under operating leases	250,330
Marine Equipment [Member] \| Barges [Member]
Operating Leased Assets [Line Items]
2018	8,711
2019	4,573
2020	3,806
2021	1,567
2022	1,567
Thereafter	896
Future minimum lease payments under operating leases	21,120
Marine Equipment [Member] \| Towing Vessels [Member]
Operating Leased Assets [Line Items]
2018	59,185
2019	8,727
2020	2,578
2021	2,578
2022	2,578
Thereafter	12,889
Future minimum lease payments under operating leases	88,535
Land Buildings and Equipment [Member]
Operating Leased Assets [Line Items]
2018	18,888
2019	15,153
2020	12,432
2021	11,384
2022	9,436
Thereafter	73,382
Future minimum lease payments under operating leases	$ 140,675

Stock Award Plans, Compensation Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Award Plans [Abstract]
Compensation cost	$ 11,460	$ 11,675	$ 11,104
Income tax benefit	$ 4,333	$ 4,378	$ 4,120

Stock Award Plans, Employee Plan Stock Option Activity (Details) - Employee Stock Award Plan [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Award Plan Information [Abstract]
Shares available for future grants (in shares)	1,805,296
Stock Options [Member]
Stock Award Plan Information [Abstract]
Term of grant	7 years
Vesting period	3 years
Outstanding Non-Qualified or Nonincentive Stock Awards [Roll Forward]
Outstanding at Period Start (in shares)	601,121	430,432	322,956
Granted (in shares)	123,141	186,706	114,894
Exercised (in shares)	(36,616)
Canceled or expired (in shares)	(32,991)	(16,017)	(7,418)
Outstanding at Period End (in shares)	654,655	601,121	430,432
Weighted Average Exercise Price [Abstract]
Outstanding at Period Start (in dollars per share)	$ 65.33	$ 71.01	$ 69.95
Granted (in dollars per share)	68.46	53.50	74.99
Exercised (in dollars per share)	47.95
Canceled or expired (in dollars per share)	74.07	80.17	86.28
Outstanding at Period End (in dollars per share)	$ 66.45	$ 65.33	$ 71.01
Stock options exercisable (in shares)	380,608	321,942	239,518
Stock Appreciation Rights [Member]
Outstanding Non-Qualified or Nonincentive Stock Awards [Roll Forward]
Outstanding at Period End (in shares)	0

Stock Award Plans, Employee Plan Outstanding and Exercisable Options (Details) - Employee Stock Award Plan [Member] - Stock Options [Member]	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
First Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	$ 46.74
Range of Exercise Prices, upper limit (in dollars per share)	$ 51.23
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	197,776
Weighted Average Remaining Contractual Life	3 years 9 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 50.02
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	100,806
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 48.86
Second Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	64.65
Range of Exercise Prices, upper limit (in dollars per share)	$ 74.99
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	394,704
Weighted Average Remaining Contractual Life	4 years
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 69.68
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	217,627
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 70.25
Third Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	93.64
Range of Exercise Prices, upper limit (in dollars per share)	$ 96.85
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	33,987
Weighted Average Remaining Contractual Life	3 years 1 month 6 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 94.31
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	33,987
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 94.31
Fourth Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	101.46
Range of Exercise Prices, upper limit (in dollars per share)	$ 104.37
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	28,188
Weighted Average Remaining Contractual Life	3 years 2 months 12 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 102.88
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	28,188
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 102.88
Full Exercise Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	46.74
Range of Exercise Prices, upper limit (in dollars per share)	$ 104.37
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	654,655
Weighted Average Remaining Contractual Life	3 years 9 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 66.45
Aggregate Intrinsic Value, Options Outstanding \| $	$ 3,455,000
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	380,608
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 69.15
Aggregate Intrinsic Value, Options Exercisable \| $	$ 1,883,000

Stock Award Plans, Employee Plan Restricted Stock Award Activity (Details) - Employee Stock Award Plan [Member] - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unvested Restricted Stock Award Shares [Roll Forward]
Nonvested balance beginning of period (in shares)	377,655	311,727	321,453
Granted (in shares)	127,255	190,610	122,740
Vested (in shares)	(105,600)	(105,109)	(113,958)
Forfeited (in shares)	(35,189)	(19,573)	(18,508)
Nonvested balance end of period (in shares)	364,121	377,655	311,727
Weighted Average Grant Date Fair Value Per Share [Abstract]
Nonvested balance beginning of period (in dollars per share)	$ 66.14	$ 75.73	$ 71.04
Granted (in dollars per share)	68.50	53.56	75.04
Vested (in dollars per share)	68.91	69.93	60.73
Forfeited (in dollars per share)	69.45	76.06	82.00
Nonvested balance end of period (in dollars per share)	$ 65.84	$ 66.14	$ 75.73

Stock Award Plans, Director Plan Stock Option Activity (Details) - Director Plan [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Award Plan Information [Abstract]
Shares available for future grants (in shares)	510,071
Stock Options [Member]
Stock Award Plan Information [Abstract]
Term of grant	10 years
Outstanding Non-Qualified or Nonincentive Stock Awards [Roll Forward]
Outstanding at Period Start (in shares)	205,429	220,429	298,334
Granted (in shares)	3,188
Exercised (in shares)	(39,000)	(9,000)	(77,905)
Canceled or expired (in shares)	(12,000)	(6,000)
Outstanding at Period End (in shares)	157,617	205,429	220,429
Weighted Average Exercise Price [Abstract]
Outstanding at Period Start (in dollars per share)	$ 64.60	$ 64.37	$ 60.01
Granted (in dollars per share)	70.65
Exercised (in dollars per share)	46.23	35.72	47.65
Canceled or expired (in dollars per share)	87.35	99.52
Outstanding at Period End (in dollars per share)	$ 67.54	$ 64.60	$ 64.37
Stock options exercisable (in shares)	156,820	205,429	220,429
Restricted Stock [Member]
Stock Award Plan Information [Abstract]
Vesting period	6 months

Stock Award Plans, Director Plan Outstanding and Exercisable Options (Details) - Director Plan [Member] - Stock Options [Member]	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
First Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	$ 29.60
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	6,000
Weighted Average Remaining Contractual Life	1 year 3 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 29.60
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	6,000
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 29.60
Second Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	41.24
Range of Exercise Prices, upper limit (in dollars per share)	$ 56.45
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	53,276
Weighted Average Remaining Contractual Life	2 years 4 months 24 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 52.77
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	53,276
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 52.77
Third Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	61.89
Range of Exercise Prices, upper limit (in dollars per share)	$ 62.48
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	35,153
Weighted Average Remaining Contractual Life	4 years 6 months
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 62.31
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	35,153
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 62.31
Fourth Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	70.65
Range of Exercise Prices, upper limit (in dollars per share)	$ 99.52
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	63,188
Weighted Average Remaining Contractual Life	6 years
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 86.50
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	62,391
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 86.71
Full Exercise Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	29.60
Range of Exercise Prices, upper limit (in dollars per share)	$ 99.52
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	157,617
Weighted Average Remaining Contractual Life	4 years 3 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 67.54
Aggregate Intrinsic Value, Options Outstanding \| $	$ 1,128,000
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	156,820
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 67.52
Aggregate Intrinsic Value, Options Exercisable \| $	$ 1,128,000

Stock Award Plans, Director Plan Restricted Stock Award Activity (Details) - Director Plan [Member] - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unvested Restricted Stock Award Shares [Roll Forward]
Nonvested balance beginning of period (in shares)	347	1,791	292
Granted (in shares)	21,198	23,074	20,350
Vested (in shares)	(21,226)	(24,518)	(18,851)
Nonvested balance end of period (in shares)	319	347	1,791
Weighted Average Grant Date Fair Value Per Share [Abstract]
Nonvested balance beginning of period (in dollars per share)	$ 64.89	$ 68.73	$ 99.52
Granted (in dollars per share)	70.65	64.89	78.52
Vested (in dollars per share)	70.56	65.17	79.77
Nonvested balance end of period (in dollars per share)	$ 70.65	$ 64.89	$ 68.73

Stock Award Plans, All Plans Options and Restricted Stock Award Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Plans Combined Disclosure [Abstract]
Intrinsic value of stock options exercised	$ 1,671	$ 266	$ 2,555
Tax benefit from stock options exercised	632	100	948
Intrinsic value of restricted stock vesting	8,485	6,928	10,270
Tax benefit from restricted stock vesting	3,208	2,598	3,810
Fair value of options vested	2,530	2,495	2,180
Fair value of restricted stock vested	$ 8,485	$ 6,928	$ 10,270
Fair value of stock options granted (in dollars per share)	$ 20.72	$ 17.30	$ 25.18
Fair value of stock options granted	$ 2,617	$ 3,231	$ 2,893
Stock Options [Member]
Share-based Compensation Plans Combined Disclosure [Abstract]
Unrecognized compensation cost related to unvested awards	$ 3,092
Weighted average period of recognition in years	1 year 3 months 18 days
Fair Value Assumptions [Abstract]
Dividend yield	0.00%	0.00%	0.00%
Average risk-free interest rate	2.00%	1.50%	1.30%
Stock price volatility	27.00%	30.00%	33.00%
Estimated option term	6 years	6 years	6 years
Restricted Stock [Member]
Share-based Compensation Plans Combined Disclosure [Abstract]
Unrecognized compensation cost related to unvested awards	$ 16,947
Weighted average period of recognition in years	3 years

Retirement Plans, Information About Plan Assets and Asset Allocation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Information about Plan Assets [Abstract]
Service period of participants not impacted by pension plan amendment	15 years
Age of plan participants not impacted by pension plan amendment	50 years
Service period of participants who are age fifty not impacted by pension plan amendment	10 years
Decrease in pension plan projected benefit obligation	$ (33,433)
Fair value of plan assets	$ 294,995	$ 257,517	$ 243,588
Expected long-term rate of return on plan assets	7.00%	7.00%	7.50%
Contribution percentage to defined contribution plan	91.00%
Asset Allocation Among Asset Categories [Abstract]
Asset allocations	100.00%	100.00%
Pension Plan [Member] \| U.S. Equity Securities [Member]
Asset Allocation Among Asset Categories [Abstract]
Asset allocations	51.00%	51.00%
Target allocations	50.00%
Pension Plan [Member] \| U.S. Equity Securities [Member] \| Minimum [Member]
Asset Allocation Among Asset Categories [Abstract]
Target allocations	30.00%
Pension Plan [Member] \| U.S. Equity Securities [Member] \| Maximum [Member]
Asset Allocation Among Asset Categories [Abstract]
Target allocations	70.00%
Pension Plan [Member] \| International Equity Securities [Member]
Asset Allocation Among Asset Categories [Abstract]
Asset allocations	21.00%	19.00%
Target allocations	20.00%
Pension Plan [Member] \| International Equity Securities [Member] \| Minimum [Member]
Asset Allocation Among Asset Categories [Abstract]
Target allocations	0.00%
Pension Plan [Member] \| International Equity Securities [Member] \| Maximum [Member]
Asset Allocation Among Asset Categories [Abstract]
Target allocations	30.00%
Pension Plan [Member] \| Debt Securities [Member]
Asset Allocation Among Asset Categories [Abstract]
Asset allocations	28.00%	30.00%
Target allocations	30.00%
Pension Plan [Member] \| Debt Securities [Member] \| Minimum [Member]
Asset Allocation Among Asset Categories [Abstract]
Target allocations	15.00%
Pension Plan [Member] \| Debt Securities [Member] \| Maximum [Member]
Asset Allocation Among Asset Categories [Abstract]
Target allocations	55.00%
Pension Plan [Member] \| Cash and Cash Equivalents [Member]
Asset Allocation Among Asset Categories [Abstract]
Asset allocations	0.00%	0.00%
Target allocations	0.00%
Pension Plan [Member] \| Cash and Cash Equivalents [Member] \| Minimum [Member]
Asset Allocation Among Asset Categories [Abstract]
Target allocations	0.00%
Pension Plan [Member] \| Cash and Cash Equivalents [Member] \| Maximum [Member]
Asset Allocation Among Asset Categories [Abstract]
Target allocations	5.00%
Other Postretirement Benefits [Member]
Information about Plan Assets [Abstract]
Fair value of plan assets	$ 0	$ 0	$ 0
Pension plan defined benefit plan cost increase limit percentage	4.00%

Retirement Plans, Schedule of Change in Benefit Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of year	$ 337,176	$ 297,325
Service cost	10,677	13,402	$ 14,683
Interest cost	13,729	14,123	13,302
Actuarial loss (gain)	34,563	19,120
Curtailments	(33,433)	0
Gross benefits paid	(7,718)	(6,794)
Benefit obligation at end of year	354,994	337,176	297,325
Accumulated benefit obligation at end of year	324,904	272,591
SERP [Member]
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of year	1,457	1,526
Service cost	0	0	0
Interest cost	58	65	64
Actuarial loss (gain)	42	12
Curtailments	0	0
Gross benefits paid	(145)	(146)
Benefit obligation at end of year	1,412	1,457	1,526
Accumulated benefit obligation at end of year	1,412	1,457
Other Postretirement Benefits [Member]
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of year	675	891
Service cost	0	0	0
Interest cost	27	29	36
Actuarial loss (gain)	52	(198)
Curtailments	0	0
Gross benefits paid	(75)	(47)
Benefit obligation at end of year	679	675	$ 891
Accumulated benefit obligation at end of year	$ 679	$ 675

Retirement Plans, Weighted-Average Assumption Used to Determine Benefit Obligation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member]
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]
Discount rate	3.70%	4.20%
Health care cost trend rate [Abstract]
Initial rate	0.00%	0.00%
Ultimate rate	0.00%	0.00%
SERP [Member]
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]
Discount rate	3.70%	4.20%
Rate of compensation increase	0.00%	0.00%
Health care cost trend rate [Abstract]
Initial rate	0.00%	0.00%
Ultimate rate	0.00%	0.00%
Other Postretirement Benefits [Member]
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]
Discount rate	3.70%	4.20%
Rate of compensation increase	0.00%	0.00%
Health care cost trend rate [Abstract]
Initial rate	7.00%	7.00%
Ultimate rate	5.00%	5.00%
Years to ultimate	2022	2021

Retirement Plans, Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation[Abstract]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Increase	$ 0	$ 0
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Decrease	0	0
SERP [Member]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation[Abstract]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Increase	0	0
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Decrease	0	0
Other Postretirement Benefits [Member]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation[Abstract]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Increase	75	74
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Decrease	(65)	(64)
Effect of one-percentage-point change in assumed health care cost trend rate on aggregate service and interest cost, Increase	3	4	$ 5
Effect of one-percentage-point change in assumed health care cost trend rate on aggregate service and interest cost, Decrease	$ (3)	$ (3)	$ (4)

Retirement Plans, Summary of Change in Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 257,517	$ 243,588
Actual return on plan assets	45,196	20,723
Employer contribution	0	0
Gross benefits paid	(7,718)	(6,794)
Fair value of plan assets at end of year	294,995	257,517
SERP [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contribution	145	146
Gross benefits paid	(145)	(146)
Fair value of plan assets at end of year	0	0
Other Postretirement Benefits [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contribution	75	47
Gross benefits paid	(75)	(47)
Fair value of plan assets at end of year	$ 0	$ 0

Retirement Plans, Summary of Funded Status at End of Year (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Funded status at end of year [Abstract]
Fair value of plan assets	$ 294,995	$ 257,517	$ 243,588
Benefit obligations	(354,994)	(337,176)	(297,325)
Funded status and amount recognized at end of year	(59,999)	(79,659)
SERP [Member]
Funded status at end of year [Abstract]
Fair value of plan assets	0	0	0
Benefit obligations	(1,412)	(1,457)	(1,526)
Funded status and amount recognized at end of year	(1,412)	(1,457)
Other Postretirement Benefits [Member]
Funded status at end of year [Abstract]
Fair value of plan assets	0	0	0
Benefit obligations	(679)	(675)	$ (891)
Funded status and amount recognized at end of year	$ (679)	$ (675)

Retirement Plans, Amounts Recognized in Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member]
Amounts recognized in the consolidated balance sheets [Abstract]
Noncurrent asset	$ 0	$ 0
Current liability	0	0
Long-term liability	(59,999)	(79,659)
SERP [Member]
Amounts recognized in the consolidated balance sheets [Abstract]
Noncurrent asset	0	0
Current liability	(159)	(150)
Long-term liability	(1,253)	(1,307)
Other Postretirement Benefits [Member]
Amounts recognized in the consolidated balance sheets [Abstract]
Noncurrent asset	0	0
Current liability	(54)	(56)
Long-term liability	$ (625)	$ (619)

Retirement Plans, Amounts Recognized in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member]
Amounts recognized in accumulated other comprehensive income [Abstract]
Net actuarial loss (gain)	$ 57,387	$ 87,658
Prior service cost (credit)	0	0
Accumulated other compensation income	57,387	87,658
SERP [Member]
Amounts recognized in accumulated other comprehensive income [Abstract]
Net actuarial loss (gain)	508	494
Prior service cost (credit)	0	0
Accumulated other compensation income	508	494
Other Postretirement Benefits [Member]
Amounts recognized in accumulated other comprehensive income [Abstract]
Net actuarial loss (gain)	(5,053)	(5,773)
Prior service cost (credit)	0	0
Accumulated other compensation income	$ (5,053)	$ (5,773)

Retirement Plans, Projected Benefit Obligation in Excess of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member]
Projected benefit obligation in excess of plan assets [Abstract]
Projected benefit obligation at end of year	$ 354,994	$ 337,176
Fair value of plan assets at end of year	294,995	257,517
SERP [Member]
Projected benefit obligation in excess of plan assets [Abstract]
Projected benefit obligation at end of year	1,412	1,457
Fair value of plan assets at end of year	$ 0	$ 0

Retirement Plans, Accumulated Benefit Obligation in Excess of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member]
Accumulated benefit obligation in excess of plan assets [Abstract]
Projected benefit obligation at end of year	$ 354,994	$ 337,176
Accumulated benefit obligation at end of year	324,904	272,591
Fair value of plan assets at end of year	294,995	257,517
SERP [Member]
Accumulated benefit obligation in excess of plan assets [Abstract]
Projected benefit obligation at end of year	1,412	1,457
Accumulated benefit obligation at end of year	1,412	1,457
Fair value of plan assets at end of year	$ 0	$ 0

Retirement Plans, Expected Employer Contribution and Benefit Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member]
Expected employer contributions [Abstract]
First year	$ 0	$ 0
Expected benefit payments (gross) [Abstract]
Year one	9,483	8,032
Year two	10,131	8,835
Year three	10,818	9,646
Year four	11,608	10,400
Year five	12,377	11,201
Next five years	75,717	70,419
SERP [Member]
Expected employer contributions [Abstract]
First year	162	153
Expected benefit payments (gross) [Abstract]
Year one	162	153
Year two	159	157
Year three	156	155
Year four	152	151
Year five	149	148
Next five years	462	514
Other Postretirement Benefits [Member]
Expected employer contributions [Abstract]
First year	48	50
Expected benefit payments (gross) [Abstract]
Year one	55	58
Year two	56	58
Year three	58	58
Year four	58	58
Year five	46	57
Next five years	$ 214	$ 199

Retirement Plans, Summary of Expected Federal Subsidy (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member]
Expected federal subsidy [Abstract]
Year one	$ 0	$ 0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Next five years	0	0
SERP [Member]
Expected federal subsidy [Abstract]
Year one	0	0
Year two	0	0
Year three	0	0
Year four	0	0
Year five	0	0
Next five years	0	0
Other Postretirement Benefits [Member]
Expected federal subsidy [Abstract]
Year one	(7)	(7)
Year two	(6)	(7)
Year three	(6)	(7)
Year four	(6)	(7)
Year five	(7)	(7)
Next five years	$ (30)	$ (33)

Retirement Plans, Components of Net Periodic Benefit Cost, Pension Benefits (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Other changes in plan assets and benefit obligations recognized in other comprehensive income [Abstract]

Recognition of actuarial loss

^[1]

$ (25,776)

$ 15,013

$ (19,482)

Recognition of prior service credit (cost)

^[1]

(3,760)

(4,763)

(6,963)

Pension Plan [Member]

Components of net periodic benefit cost [Abstract]

Service cost

10,677

13,402

14,683

Interest cost

13,729

14,123

13,302

Expected return on plan assets

(18,195)

(16,805)

(17,921)

Actuarial loss (gain)

4,400

5,484

7,728

Prior service credit

Net periodic benefit cost

10,611

16,204

17,792

Other changes in plan assets and benefit obligations recognized in other comprehensive income [Abstract]

Current year actuarial loss (gain)

7,562

15,203

(19,127)

Recognition of actuarial loss

(37,833)

(5,484)

(7,728)

Recognition of prior service credit (cost)

Total recognized in other comprehensive income

(30,271)

9,719

(26,855)

Total recognized in net periodic benefit cost and other comprehensive income

(19,660)

25,923

(9,063)

SERP [Member]

Components of net periodic benefit cost [Abstract]

Service cost

Interest cost

Expected return on plan assets

Actuarial loss (gain)

Prior service credit

Net periodic benefit cost

Other changes in plan assets and benefit obligations recognized in other comprehensive income [Abstract]

Current year actuarial loss (gain)

(30)

Recognition of actuarial loss

(28)

(26)

(28)

Recognition of prior service credit (cost)

Total recognized in other comprehensive income

(14)

(58)

Total recognized in net periodic benefit cost and other comprehensive income

$ 100

$ 77

$ 34

[1]	Actuarial gains (losses) are amortized into costs of sales and operating expenses or selling, general and administrative expenses as appropriate. (See Note 10 - Retirement Plans).

Retirement Plans, Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost, Pension Benefits (Details)

3 Months Ended

9 Months Ended

12 Months Ended

Apr. 11, 2017

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Pension Benefits [Member]

Weighted average assumptions used to determine net periodic benefit cost [Abstract]

Discount rate

^[1]

4.20%

4.00%

4.50%

4.10%

Expected long-term rate of return on plan assets

7.00%

7.50%

Rate of compensation increase

4.25%

SERP [Member]

Weighted average assumptions used to determine net periodic benefit cost [Abstract]

Discount rate

^[1]

4.20%

4.50%

4.10%

Expected long-term rate of return on plan assets

0.00%

Rate of compensation increase

0.00%

[1]	The 2017 benefit cost for the pension plan was determined using a discount rate of 4.2% for the period beginning January 1, 2017 and ending April 11, 2017 and 4.0% for the period beginning April 12, 2017 and ending December 31, 2017.

Retirement Plans, Estimated Amounts That Will be Amortized from AOCI Into Net Periodic Benefit Cost, Pension Benefits (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ 2,820
Prior service cost (credit)	0
Estimated amounts to be amortized	2,820
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	23
Prior service cost (credit)	0
Estimated amounts to be amortized	$ 23

Retirement Plans, Components of Net Periodic Benefit Cost, Other Postretirement Benefits (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Other changes in plan assets and benefit obligations recognized in other comprehensive income [Abstract]

Recognition of actuarial gain

^[1]

$ (25,776)

$ 15,013

$ (19,482)

Recognition of prior service credit (cost)

^[1]

(3,760)

(4,763)

(6,963)

Retirement Plans, Estimated Amounts That Will be Amortized from AOCI Into Net Periodic Benefit Cost, Other Postretirement Benefits (Details) - Other Postretirement Benefits [Member] $ in Thousands	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain	$ (596)
Prior service cost	0
Estimated amounts to be amortized	$ (596)

Contingencies and Commitments (Details)	12 Months Ended
Contingencies and Commitments (Details)	Dec. 31, 2017 PotentiallyResponsibleParty Spill BargeSlip Lawsuit Plaintiff	Mar. 22, 2014 Vessel TankBarge
Collision with M/S Summer Wind [Member]
Loss Contingencies [Line Items]
Number of vessels involved in collision \| Vessel		2
Number of vessels damaged in collision resulting in fuel oil discharge \| TankBarge		1
Number of actions filed against the Company \| Lawsuit	2
Number of crewmembers alleging damages \| Plaintiff	2
Portland Harbor Superfund Site [Member]
Site Contingency [Line Items]
Number of other companies also named as Potentially Responsible Parties ("PRPs") \| PotentiallyResponsibleParty	250
Number of spills \| Spill	4
SBA Shipyard Site [Member]
Site Contingency [Line Items]
Number of barge slips \| BargeSlip	3

Contingencies and Commitments, Certain Significant Risks and Uncertainties (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Customers Distributor	Dec. 31, 2016 Customers	Dec. 31, 2015 Customers
Guaranties [Abstract]
Issued guaranties	$ 21,554
Maximum [Member]
Guaranties [Abstract]
Guarantor obligations, expiration period	4 years
Performance Bonds [Member]
Guaranties [Abstract]
Issued guaranties	$ 11,316
Marine Transportation [Member]
Certain Significant Risks and Uncertainties [Abstract]
Percentage of inland revenue	75.00%
Marine Transportation [Member] \| Minimum [Member]
Certain Significant Risks and Uncertainties [Abstract]
Range of renewal options under term contracts	1 year
Marine Transportation [Member] \| Maximum [Member]
Certain Significant Risks and Uncertainties [Abstract]
Range of renewal options under term contracts	5 years
Marine Transportation [Member] \| Customers [Member]
Certain Significant Risks and Uncertainties [Abstract]
Percentage of costal revenue	80.00%
Customer relationship period	40 years
Number of single customers accounting more than 10% of segment revenue \| Customers	0	0	0
Distribution and Services [Member]
Certain Significant Risks and Uncertainties [Abstract]
Number of off-highway top distributors \| Distributor	5
Services segment's relationship term	52 years
Distribution and Services [Member] \| Customers [Member]
Certain Significant Risks and Uncertainties [Abstract]
Number of single customers accounting more than 10% of segment revenue \| Customers	0	0	0
Letters Of Credit [Member]
Guaranties [Abstract]
Issued guaranties	$ 10,238

Segment Data (Details) $ in Thousands	3 Months Ended								12 Months Ended
Segment Data (Details) $ in Thousands	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Data [Abstract]
Number of reportable segments \| Segment									2
Revenues [Abstract]
Revenues	$ 708,111	$ 541,274	$ 473,328	$ 491,705	$ 435,650	$ 434,708	$ 441,582	$ 458,733	$ 2,214,418	$ 1,770,673	$ 2,147,532
Segment profit (loss)	(58,860)	47,861	43,015	40,998	52,370	51,559	62,474	61,343	73,014	227,746	361,712
Total assets	5,127,427				4,289,895				5,127,427	4,289,895	4,140,558
Depreciation and amortization									202,881	200,917	192,240
Capital expenditures									177,222	231,066	345,475
Other segment disclosures [Abstract]
Interest expense	(7,162)	(5,388)	(4,465)	(4,457)	(4,477)	(4,507)	(4,513)	(4,193)	(21,472)	(17,690)	(18,738)
Impairment of long-lived assets	(105,712)								(105,712)	0	0
Gain (loss) on disposition of assets	(4,288)	(159)	(139)	99	(166)	(122)	94	67	(4,487)	(127)	1,672
Other income (expense)	469	$ (113)	$ (1)	$ (116)	47	$ (120)	$ 179	$ 135	(52)	(291)	(663)
Profit (loss) from other segment									(149,582)	(32,542)	(32,051)
Details of "Other" total assets [Abstract]
Investment in affiliates	1,890				2,622				1,890	2,622
Other [Member]
Revenues [Abstract]
Segment profit (loss)									(149,582)	(32,542)	(32,051)
Total assets	75,243				52,676				75,243	52,676	63,009
Depreciation and amortization									3,596	3,793	3,944
Capital expenditures									6,715	7,728	4,706
Other segment disclosures [Abstract]
General corporate expenses									(18,150)	(14,966)	(14,773)
Interest expense									(21,472)	(17,690)	(18,738)
Impairment of long-lived assets									(105,712)	0	0
Gain (loss) on disposition of assets									(4,487)	(127)	1,672
Other income (expense)									239	241	(212)
Details of "Other" total assets [Abstract]
General corporate assets	73,353				50,054				73,353	50,054	60,919
Investment in affiliates	1,890				2,622				1,890	2,622	2,090
Total other assets	75,243				52,676				75,243	52,676	63,009
Reportable Segments [Member] \| Marine Transportation [Member]
Revenues [Abstract]
Revenues									1,324,106	1,471,893	1,663,090
Segment profit (loss)									136,011	257,102	374,842
Total assets	3,485,099				3,613,951				3,485,099	3,613,951	3,444,785
Depreciation and amortization									178,898	184,291	175,798
Capital expenditures									165,421	217,423	311,862
Reportable Segments [Member] \| Distribution and Services [Member]
Revenues [Abstract]
Revenues									890,312	298,780	484,442
Segment profit (loss)									86,585	3,186	18,921
Total assets	$ 1,567,085				$ 623,268				1,567,085	623,268	632,764
Depreciation and amortization									20,387	12,833	12,498
Capital expenditures									5,086	5,915	28,907
Intersegment Eliminations [Member]
Revenues [Abstract]
Revenues									20,717	24,672	26,203
Segment profit (loss)									$ 2,072	$ 2,467	$ 2,620

Subsequent Events (Details) - Subsequent Event [Member] $ in Thousands, bbl in Millions	Feb. 14, 2018 USD ($) bbl Towboat TankBarge	Feb. 12, 2018 USD ($)
Senior Notes Due March 01, 2028 [Member]
Subsequent Event [Line Items]
Long term debt, face amount		$ 500,000
Debt instrument, interest rate, stated percentage		4.20%
Credit facility, expiration date		Mar. 01, 2028
Periodic payment, interest		$ 10,500
Periodic payment, interest, exception of first payment		$ 11,550
Higman [Member]
Subsequent Event [Line Items]
Cash paid for acquisition	$ 419,692
Tank barge barrel capacity \| bbl	4,800,000
Higman [Member] \| Inland Tank Barges [Member]
Subsequent Event [Line Items]
Number of maritime vessels acquired \| TankBarge	159
Number of maritime vessels under construction \| TankBarge	2
Higman [Member] \| Inland Towboats [Member]
Subsequent Event [Line Items]
Number of maritime vessels acquired \| Towboat	75