Cover [Abstract] Entity Address, Address Line One Entity Address, Address Line Two Entity Address, Address Line Three Amendment Flag City Area Code Entity Address, City or Town Entity Address, Country Current Fiscal Year End Date Document Period End Date Entity Incorporation, State or Country Code Entity Information, Former Legal or Registered Name Local Phone Number Entity Address, Postal Zip Code Entity Address, State or Province Title of 12(b) Security No Trading Symbol Flag Trading Symbol Security Exchange Name Entity Current Reporting Status Entity Filer Category Entity Registrant Name Entity Central Index Key Entity Tax Identification Number Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Document Type Document Quarterly Report Document Transition Report Entity Interactive Data Current Entity File Number Entity Shell Company Entity Emerging Growth Company Entity Small Business Award Type [Axis] ASU 2018-02 [Member] Accounting Standards Update 2018-02 [Member] ASU 2016-02 [Member] Accounts payable Trade - less allowance for doubtful accounts Accounts Receivable, after Allowance for Credit Loss, Current Accounts receivable: Accounts Receivable, after Allowance for Credit Loss, Current [Abstract] Accrued liabilities Income taxes payable Accrued Income Taxes, Current Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Accumulated other comprehensive income - net Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated Other Comprehensive Income [Member] AOCI Attributable to Parent [Member] Weighted average amortization period of intangibles Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Additional Paid-in Capital [Member] Additional Paid-in Capital [Member] Additional paid-in capital Adjustments to reconcile net earnings to net cash provided by operations: Tax withholdings on equity award vesting Share-based Payment Arrangement, Decrease for Tax Withholding Obligation Adjustments for New Accounting Pronouncements [Axis] Other [Member] Other Segments [Member] Compensation cost Share-based Payment Arrangement, Expense Amortization of debt issuance costs Antidilutive securities excluded from computation of earnings per share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount ASSETS Assets [Abstract] Total assets Total assets Assets Total current assets Assets, Current Current assets: Alternate Base Rate [Member] Base Rate [Member] BASIS FOR PREPARATION OF THE CONDENSED FINANCIAL STATEMENTS Basis of Accounting [Text Block] Prepaid expenses Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets Assets [Abstract] Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract] Purchase consideration Other long-term liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other Other intangibles Total assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Business Acquisition [Line Items] Business Acquisition [Axis] ACQUISITIONS [Abstract] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Acquisitions [Abstract] Business Combination, Separately recognized Transactions, Additional Disclosures [Abstract] Property and equipment ACQUISITIONS Business Combination Disclosure [Text Block] Fair values of assets acquired and liabilities assumed, net [Abstract] Acquisition related costs Business Combination, Acquisition Related Costs Net assets acquired Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net Cash and cash equivalents, beginning of year Cash and cash equivalents, end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash acquired in acquisition Cash Acquired from Acquisition Cash and cash equivalents Increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Contingencies and commitments Commitments and Contingencies CONTINGENCIES [Abstract] CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Common Stock [Member] Common Stock [Member] Common stock, par value per share (in dollars per share) Common stock, shares issued (in shares) Common stock, shares authorized (in shares) Common stock, $0.10 par value per share. Authorized 120,000,000 shares, issued 65,472,000 shares Common Stock, Value, Issued RETIREMENT PLANS [Abstract] Comprehensive income attributable to Kirby Comprehensive Income (Loss), Net of Tax, Attributable to Parent Total comprehensive income, net of taxes Total comprehensive income, net of taxes Revenue recognized Deferred revenues Contract assets Total costs and expenses Costs and Expenses Costs and expenses: Costs and Expenses [Abstract] Credit Facility [Domain] Credit Facility [Axis] Adoption of new accounting standards Cumulative Effect of New Accounting Principle in Period of Adoption Current Current State and Local Tax Expense (Benefit) Foreign - current State and local [Abstract] Current Current Federal Tax Expense (Benefit) Revenues by Major Source Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Table] Disaggregation of Revenue [Abstract] Term of loan Basis spread on variable rate LONG-TERM DEBT [Abstract] Schedule of Long-term Debt Instruments [Table] Senior Notes outstanding Debt Instrument [Line Items] Estimated fair value of outstanding debt Debt instrument, frequency of periodic payment Performance Bonds [Member] Debt Securities Payable [Member] Long-term Debt [Abstract] Debt Instruments [Abstract] Tax benefit from stock options exercised Deferred Tax Expense from Stock Options Exercised Deferred Deferred Federal Income Tax Expense (Benefit) Provision for deferred income taxes Deferred Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Retirement Plans [Abstract] Defined Benefit Plan, Additional Information [Abstract] Amortization of actuarial loss Defined Benefit Plan, Amortization of Gain (Loss) Defined Benefit Plan Disclosure [Line Items] Pension contributions Defined Benefit Plan, Plan Assets, Contributions by Employer Components of net periodic benefit cost [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Net periodic benefit cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Interest cost Defined Benefit Plan, Interest Cost Decrease in pension plan projected benefit obligation Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment Service cost Defined Benefit Plan, Service Cost Depreciation and amortization STOCK AWARD PLANS [Abstract] STOCK AWARD PLANS Share-based Payment Arrangement [Text Block] United States [Member] Domestic Tax Authority [Member] Net earnings per share attributable to Kirby common stockholders: Net earnings per share attributable to Kirby common stockholders [Abstract] EARNINGS PER SHARE Earnings Per Share [Text Block] Diluted (in dollars per share) Diluted (in dollars per share) Basic (in dollars per share) Basic (in dollars per share) EARNINGS PER SHARE [Abstract] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Income tax benefit Share-based Payment Arrangement, Expense, Tax Benefit Unrecognized compensation cost related to unvested awards Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Weighted average period of recognition in years Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Stock Options [Member] Equity Component [Domain] Equity Component [Domain] Fair Value, Inputs, Level 1, 2 and 3 [Member] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Axis] Level 2 [Member] Federal [Abstract] Federal Income Tax Expense (Benefit), Continuing Operations [Abstract] Fair Value Measurements [Abstract] Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Other intangibles - net Foreign [Member] Foreign Tax Authority [Member] (Gain) loss on disposition of assets Gain (loss) on disposition of assets Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Goodwill Goodwill Guarantor Obligations [Line Items] Guarantor Obligations, Nature [Axis] Issued guaranties Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Nature [Domain] Guaranties [Abstract] Guarantees [Abstract] Intersegment Eliminations [Member] Income Approach [Member] Income Tax Authority [Axis] TAXES ON INCOME [Abstract] Earnings before taxes on income Earnings (loss) before taxes on income Segment profit (loss) CONDENSED STATEMENTS OF EARNINGS (Unaudited) [Abstract] Earnings (loss) before taxes on income [Abstract] TAXES ON INCOME Provision for taxes on income Total Provision for taxes on income Income Tax Expense (Benefit) Income Tax Authority [Domain] Income taxes paid Income Taxes Paid, Net Increase (decrease) in cash flows resulting from changes in operating assets and liabilities, net Increase (Decrease) in Operating Capital Increase (Decrease) in Stockholders' Equity [Roll Forward] Dilutive effect of stock options and restricted stock units (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Interest expense Interest Expense Interest paid Finished goods INVENTORIES [Abstract] INVENTORIES Inventory Disclosure [Text Block] Inventory, Net, Total Inventories - net Inventory, Net Work in process Details of inventories [Abstract] Inventory, Net [Abstract] Investment in affiliates Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures LIBOR [Member] LEASES Thereafter Lessee, Operating Lease, Liability, Payments, Due after Year Five 2022 Lessee, Operating Lease, Liability, Payments, Due Year Four 2023 Lessee, Operating Lease, Liability, Payments, Due Year Five Total lease payments Liabilities for operating leases Future Minimum Lease Payments under Operating Leases 2019 Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year Less: imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount 2021 Lessee, Operating Lease, Liability, Payments, Due Year Three 2020 Lessee, Operating Lease, Liability, Payments, Due Year Two Lease Cost [Abstract] Total lease cost Lease, Cost Lease Cost LEASES [Abstract] Letter of Credit [Member] LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities and Equity [Abstract] Total liabilities and equity Liabilities and Equity Total long-term liabilities Liabilities, Noncurrent Current liabilities: Total current liabilities Liabilities, Current Credit facility, amount outstanding Credit facility, expiration date Line of Credit Facility, Expiration Date Commitment amount Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity LONG-TERM DEBT Long-term debt, net - less current portion Long-term Debt, Excluding Current Maturities Loss Contingency [Abstract] Loss Contingencies [Line Items] Loss Contingency Nature [Axis] Loss Contingencies [Table] Loss Contingency, Nature [Domain] Return of investment to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Noncontrolling interests Net Income (Loss) Attributable to Parent [Abstract] Net Income (Loss) Attributable to Parent [Abstract] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Cash flows from operating activities: Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Net earnings attributable to Kirby Net earnings attributable to Kirby Net Income (Loss) Attributable to Parent Income available to Kirby common stockholders - basic Net Income (Loss) Available to Common Stockholders, Basic Cash flows from financing activities: Income available to Kirby common stockholders - diluted Net Income (Loss) Available to Common Stockholders, Diluted Less: Net earnings attributable to noncontrolling interests Net earnings attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest New Accounting Pronouncements or Change in Accounting Principle [Line Items] ACCOUNTING STANDARDS ADOPTIONS New Accounting Pronouncements, Policy [Policy Text Block] New Accounting Pronouncements [Abstract] New Accounting Pronouncement or Change in Accounting Principle, Retrospective Adjustments [Abstract] ACCOUNTING STANDARDS ADOPTIONS [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] ACCOUNTING STANDARDS ADOPTIONS Other income Other income Bank notes payable Number of reportable segments Number of Reportable Segments Noncontrolling Interests [Member] Noncontrolling Interest [Member] Oil and Gas [Member] Future Minimum Lease Payments Under Operating Leases [Abstract] Weighted average remaining lease term Operating lease right-of-use assets Right-of-use assets Operating lease cost Operating Lease, Cost Reporting Segments [Member] Operating Segments [Member] Weighted average discount rate Operating income Operating Income (Loss) Current portion of operating lease liabilities Operating lease liabilities Operating cash outflow from operating leases 2019 Operating lease liabilities Operating Lease, Liability 2020 Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2023 2022 2021 Future minimum lease payments under operating leases Operating Leases, Future Minimum Payments Due Thereafter Actuarial gains (losses), Net Amount Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Actuarial gains (losses), Income Tax (Provision) Benefit Amortization of net actuarial loss, Net Amount Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax Actuarial gains (losses), Gross Amount Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax Amortization of net actuarial loss, Income Tax (Provision) Benefit Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax Amortization of net actuarial loss, Gross Amount Foreign currency translation, Income Tax (Provision) Benefit Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Foreign currency translation adjustments Foreign currency translation, Net Amount Pension and postretirement benefits Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Total other comprehensive income, Gross Amount Other Comprehensive Income (Loss), before Tax Foreign currency translation, Gross Amount Total other comprehensive income (loss), net of taxes Other Comprehensive Income (Loss), Net of Tax OTHER COMPREHENSIVE INCOME Other Comprehensive Income, Noncontrolling Interest [Text Block] Other Other Noncash Income (Expense) Details of "Other" total assets [Abstract] Total other assets Other Assets Total other comprehensive income, Income Tax (Provision) Benefit Other Comprehensive Income (Loss), Tax Pension and postretirement benefits [Abstract] Other comprehensive income (loss), net of taxes: Other assets Other Assets, Noncurrent OTHER COMPREHENSIVE INCOME [Abstract] Other long-term liabilities Other Postretirement Benefits [Member] Other Postretirement Benefits [Member] Other Other Receivables Payments related to tax withholding for share-based compensation Payment, Tax Withholding, Share-based Payment Arrangement Acquisitions of businesses and marine equipment, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Payments of debt issue costs Payments of Debt Issuance Costs Capital expenditures Purchase price Payments to Acquire Productive Assets Pension Plan [Member] Pension Plan [Member] RETIREMENT PLANS Pension and Other Postretirement Benefits Disclosure [Text Block] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Prepaid expenses and other current assets Other Payments on bank credit facilities Proceeds from (Repayments of) Lines of Credit Borrowings on long-term debt Proceeds from disposition of assets Proceeds from exercise of stock options Net earnings Net earnings Property and equipment Property, Plant and Equipment, Gross Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property and equipment - net Property, Plant and Equipment, Net Right-of-use assets obtained in exchange for lease obligations Payments on long-term debt Payments on long-term debt Repayments of Long-term Debt Restricted Stock [Member] RSUs [Member] Retained Earnings [Member] Retained Earnings [Member] Retained earnings Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Revenue, Performance Obligation [Abstract] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] REVENUES [Abstract] Expected timing of satisfaction, period REVENUES Revenue from Contract with Customer [Text Block] Total revenues Revenues by major source Revenues Revenues: Revolving Credit Facility [Member] Sublease income Sublease Income Intrinsic value of restricted stock vesting Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested Weighted Average Exercise Price, Options Outstanding (in dollars per share) Weighted Average Exercise Price, Options Exercisable (in dollars per share) Fair value of options vested Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value Estimated option term Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Aggregate Intrinsic Value, Options Exercisable Weighted Average Remaining Contractual Life Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Details of Inventories Stock Option Valuation Assumptions Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Stock Option Activity Share-based Payment Arrangement, Option, Activity [Table Text Block] Fair Values of Assets Acquired and Liabilities Assumed Restricted Stock Award Activity Share-based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] Earnings Before Taxes Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] RSU Activity Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Compensation Cost Breakdown in Statement of Earnings Basic and Diluted Earnings per Share Changes in Other Comprehensive Income Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Net Periodic Benefit Cost Schedule of Defined Benefit Plans Disclosures [Table Text Block] Schedule of Guarantor Obligations [Table] Segment Reporting Information, by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Outstanding and Exercisable Stock Options Share-based Payment Arrangement, Option, Exercise Price Range [Table Text Block] SEGMENT DATA Segment Reporting Disclosure [Text Block] Segment Reporting Information [Line Items] Segments [Domain] SEGMENT DATA [Abstract] Revenues [Abstract] Segment Reporting Information, Revenue for Reportable Segment [Abstract] Selling, general and administrative Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Amortization of unearned share-based compensation Share-based Payment Arrangement, Noncash Expense Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Share-Based Compensation Arrangement By Share-Based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Canceled or expired (in dollars per share) Term of grant Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period Granted (in shares) Dividend yield Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Fair value of restricted stock vested Vested (in shares) Vesting (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Unvested Restricted Stock Award Shares [Roll Forward] Unvested RSU Shares [Roll Forward] Unvested balance beginning of period (in shares) Unvested balance end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Unvested balance beginning of period (in dollars per share) Unvested balance end of period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in dollars per share) Stock price volatility Vested (in dollars per share) Weighted Average Grant Date Fair Value Per Share [Abstract] Fair Value Assumptions [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Fair value of stock options granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Shares available for future grants (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Intrinsic value of stock options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Average risk-free interest rate Outstanding Non-Qualified or Nonincentive Stock Awards [Roll Forward] Outstanding Non-Qualified or Nonincentive Stock Options [Roll Forward] Canceled or expired (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Weighted Average Exercise Price [Abstract] Equity Award [Domain] Outstanding at Period End (in shares) Outstanding at Period Start (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Outstanding at Period Start (in dollars per share) Outstanding at Period End (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Aggregate Intrinsic Value, Options Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Exercise Price Range [Axis] Range of Exercise Prices, lower limit (in dollars per share) Share-based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit Range of Exercise Prices, upper limit (in dollars per share) Number Outstanding (in shares) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain] Number Exercisable (in shares) Tax withholdings on equity award vesting (in shares) Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation Beginning balance (in shares) Ending balance (in shares) Shares, Outstanding Short-term lease cost Letters of Credit [Member] Standby Letters of Credit [Member] CONDENSED BALANCE SHEETS (Unaudited) [Abstract] CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) [Abstract] Equity Components [Axis] Statement [Line Items] Statement [Table] Segments [Axis] CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) [Abstract] CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) [Abstract] Stock Appreciation Rights [Member] Stock Appreciation Rights (SARs) [Member] Stock option exercises (in shares) Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Issuance of stock for equity awards, net of forfeitures (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Stock option exercises Stock Issued During Period, Value, Stock Options Exercised Issuance of stock for equity awards, net of forfeitures Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Equity: Total Kirby stockholders' equity Stockholders' Equity Attributable to Parent Beginning balance Ending balance Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Kirby stockholders' equity: Subsequent Event [Table] SUBSEQUENT EVENT Subsequent Event [Member] Subsequent Event Type [Domain] Subsequent Event [Line Items] SUBSEQUENT EVENT [Abstract] Subsequent Event Type [Axis] Supplemental disclosures of cash flow information: Supplemental Cash Flow Information [Abstract] SERP [Member] Supplemental Employee Retirement Plan [Member] Reclassification to retained earnings of stranded tax effects from tax reform Tax Cuts and Jobs Act, Change in Tax Rate, Income Tax Expense (Benefit) Reclassification to retained earnings of stranded tax effects from tax reform, Income Tax (Provision) Benefit Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect Taxes, other than on income Taxes, Miscellaneous Treasury stock, shares (in shares) Treasury stock - at cost, 5,544,000 shares at September 30, 2019 and 5,608,000 at December 31, 2018 Treasury Stock, Value Treasury Stock [Member] Treasury Stock [Member] Type of Adoption [Domain] Underlying Asset Class [Domain] Underlying Asset Class [Axis] Collision with M/S Summer Wind [Member] Undistributed earnings allocated to restricted shares Undistributed Earnings (Loss) Allocated to Participating Securities, Basic Undistributed earnings allocated to restricted shares Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted Valuation Approach and Technique [Axis] Valuation Approach and Technique [Domain] Variable Rate [Domain] Variable lease cost Variable Rate [Axis] Weighted average unvested restricted stock (in shares) Weighted Average Number of Shares, Restricted Stock Weighted average common stock outstanding - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Weighted average common stock outstanding - diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Consolidation Items [Domain] Consolidation Items [Axis] Products and Services [Domain] Products and Services [Axis] BASIS FOR PREPARATION OF THE CONDENSED FINANCIAL STATEMENTS [Abstract] Marine transportation - A component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. Marine Transportation [Member] Marine Transportation [Member] Costs incurred and are directly related to generating revenues and generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services, excludes selling, general and administrative expense. Costs Of Sales And Operating Expenses Costs of sales and operating expenses Distribution and services - A component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. Distribution And Services [Member] Distribution and Services [Member] Refers to coastal transportation of refined petroleum products and black oil. Coastal Transportation [Member] Coastal Transportation [Member] Refers to inland transportation of petrochemical feedstock, chemicals, pressurized products, refined petroleum products, certain black oil, agricultural chemicals and black oil, such as asphalt. Inland Transportation [Member] Inland Transportation [Member] Refers to selling OEM replacement parts and new diesel engines, provides service mechanics and maintains facilities to overhaul and repair diesel engines and ancillary products for marine and on-highway transportation companies, mining and industrial companies. The Company provides engineering and field services, OEM replacement parts and safety-related products to power generation operators and to the nuclear industry, manufactures engine generator and pump packages for power generation operators and municipalities, offers power generation systems customized for specific commercial and industrial applications, and rents equipment including power generation systems, pumps, air compressors, fork lifts and railcar movers. Commercial and Industrial [Member] Commercial and Industrial [Member] A credit facility arrangement that is repayable in quarterly installments in increasing percentages of the original principal amount of the loan. Term Loan Facility [Member] Term Loan [Member] Percentage of unpaid principal balance payable on initial amount. Unpaid Balance Payable on Initial Amount, Percentage Percentage of unpaid balance payable on initial amount Cash paid during the period [Abstract] Cash paid during the period: Other income (expense) included in net income that results in no cash inflows or outflows in the period. Includes noncash adjustments to reconcile net income (loss) to cash provided by (used in) operating activities that are not separately disclosed. Amortization of Major Maintenance Costs Amortization of major maintenance costs Amount of amortization expense attributable to right-of-use asset from operating lease. Operating Lease, Right-of-Use Asset, Amortization Amortization of leases Current and future cash outflow to pay for purchases of fixed assets that have occurred. Capital Expenditures Incurred, Paid and Not yet Paid Capital expenditures included in accounts payable Non-cash investing activity: [Abstract] Non-cash investing activity: Refers to the amount related to amortization of unearned compensation. Amortization of unearned compensation Amortization of unearned share-based compensation Undistributed Earnings Reallocated To Restricted Shares. Undistributed Earnings Reallocated To Restricted Shares Undistributed earnings reallocated to restricted shares Shares Outstanding [Abstract] Shares outstanding [Abstract] Number of shares of common stock determined by relating the portion of time within a reporting period that common shares have been issued and outstanding to the total time in that period. Weighted average common stock issued and outstanding Weighted average common stock issued and outstanding (in shares) Weighted average amortization period of unfavorable contracts in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Weighted Average Useful Life, Unfavorable Contracts Weighted average amortization period of unfavorable contracts Refers to the number of maritime (seagoing) vessels acquired. Number of Maritime Vessels Acquired Number of maritime vessels acquired The average age of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. Property, Plant and Equipment, Average Age Average age of property Refers to the entity that is being acquired or purchased in a merger or acquisition. Cenac Marine Services, LLC [Member] Refers to the aggregate carrying capacity of a quantity of tank barges as measured in number of barrels. Tank Barge Aggregate Barrel Capacity Aggregate tank barge barrel capacity (in barrels) Refers to the carrying capacity of tank barges as measured in number of barrels. Tank Barge Barrel Capacity Tank barge barrel capacity (in barrels) Small powerful boat designed for towing or pushing larger vessels. Tugboats [Member] Offshore Tugboats [Member] Refers to inland tank barges equipped with tanks that may carry any one of a great variety of liquid commodities, such as petroleum and petroleum products, chemicals, and fertilizers. Inland Tank Barges [Member] Inland Tank Barges [Member] Refers to barrel tank barges equipped with tanks that may carry any one of a great variety of liquid commodities, such as petroleum and petroleum products, chemicals, and fertilizers. Barrel Tank Barges [Member] Inland Barrel Tank Barges [Member] Refers to a diesel-powered or steam-powered boat used especially on inland waterways to push groups of barges lashed to it in front or on one side or both. Inland Towboats [Member] Inland Towboats [Member] Restricted Stock Award Activity [Abstract] Represents to director plan of the equity-based compensation arrangement plan. Director Plan [Member] Director Plan [Member] Other Supplemental Information about Operating Leases [Abstract] Other Supplemental Information about Operating Leases [Abstract] Estimated percentage of costs related to service costs and other non-lease components. Percentage of Costs related to Service Costs Estimated Percentage of costs relate to service costs for leased towing vessels operating leases related to weighted average discount rate and weighted average remaining lease term. Operating Leases, Weighted Average Discount Rate and Remaining Lease Term [Table Text Block] Operating Leases, Weighted Average Discount Rate and Remaining Lease Term Represents to employee plan of the equity-based compensation arrangement plan. Employee Plan [Member] Employee Stock Award Plan [Member] Restricted Stock Unit Activity [Abstract] RSU Activity [Abstract] Outstanding and Exercisable Stock options [Abstract] Share based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Outstanding Options [Abstract] Options Outstanding [Abstract] Share based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Exercisable Options [Abstract] Options Exercisable [Abstract] Represents information of second price range of option prices pertaining to options granted. Second Price Range [Member] Second Price Range [Member] Represents information of first price range of option prices pertaining to options granted. First Price Range [Member] First Price Range [Member] This is the total range, encompassing the minimum exercise price amount, and the maximum exercise price amount. Its child Members should disaggregate the individual tranches of price ranges. Total Exercise Price Range [Member] Full Exercise Price Range [Member] Represents information of third price range of option prices pertaining to options granted. Third Price Range [Member] Third Price Range [Member] A table disclosing the information about earnings (loss) before taxes on income. Income Tax Disclosure [Table] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Income Tax Disclosure [Line Items] Provision for taxes on income [Abstract] Provision for taxes on income [Abstract] The service period of eligible participants of the employee pension plan who have reached the age of fifty that will be grandfathered and not be impacted by the amendment to the pension plan. Employee Pension Plan, Grandfathered Participants, Participant Service Period Who is Fifty Years Old Service period of participants who are age fifty not impacted by pension plan amendment The age of eligible participants of the employee pension plan who will be grandfathered and not be impacted by the amendment to the pension plan. Employee Pension Plan, Grandfathered Participants, Participant Age Age of plan participants not impacted by pension plan amendment Refers to percentage of pension plan defined benefit plan cost increase limit during the period. Pension Plan Defined Benefit Plan Cost Increase Limit Percentage Pension plan defined benefit plan cost increase limit percentage The service period of eligible participants of the employee pension plan who will be grandfathered and not be impacted by the amendment to the pension plan. Employee Pension Plan, Grandfathered Participants, Service Period Service period of participants not impacted by pension plan amendment Refers to the entity that is being acquired or purchased in a merger or acquisition. Higman Marine, Inc [Member] Higman [Member] A claim for damages that is likely to be made and for which it is reasonably possible that there will be an unfavorable outcome, such as a likelihood that lawsuits from parties as yet unidentified will be filed alleging injury from using a product when other parties have successfully sued the entity for such use. Unasserted Claim 1 [Member] Struck by LPG Tanker, the Genesis River [Member] Number of vessels damaged in collision resulting in fuel oil discharge. Number of vessels damaged in collision resulting in fuel oil discharge Refers to the number of maritime (seagoing) vessels. Number of Maritime Vessels Number of vessels involved in collision Employee Stock Award Plan [Abstract] Stock Award Plan Information [Abstract] Refers to amount of fair value of options granted during the period. Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Fair Value Fair value of stock options granted Tax benefit from restricted stock vesting during the reporting period. Tax Benefit From Restricted Stock Vesting Tax benefit from restricted stock vesting Share based Compensation Plans Combined Disclosure [Abstract] Represents information of fourth price range of option prices pertaining to options granted. Fourth Price Range [Member] Fourth Price Range [Member] Tabular disclosure of the profit or loss and total assets for other segment information. Schedule Of Other Segment Reporting Information By Segment [Table Text Block] Other Segment Reporting Information Assets other than goodwill that contribute to the future cash flows of both the cash-generating unit under review and other cash-generating units. General corporate assets Other segment disclosure [Abstract] Other segment disclosures [Abstract] Refers to amount of general corporate expenses. General corporate expenses General corporate expenses Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of before tax from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act. Tax Cuts and Jobs Act, Other Comprehensive (Income) Loss, Reclassification from AOCI to Retained Earnings, Before Tax Reclassification to retained earnings of stranded tax effects from tax reform, Gross Amount Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of net of tax from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act. Tax Cuts and Jobs Act, Other Comprehensive (Income) Loss, Reclassification from AOCI to Retained Earnings, Net of Tax Reclassification to retained earnings of stranded tax effects from tax reform, Net Amount Subsequent Event [Abstract] Subsequent Event [Abstract]