Kirby (KEX) 10-K20 Feb 242023 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
Document and Entity Information - USD ($) $ in Billions	Dec. 31, 2023	Feb. 16, 2024	Jun. 30, 2023
Cover [Abstract]
Entity Registrant Name	Kirby Corporation
Entity Central Index Key	0000056047
Current Fiscal Year End Date	--12-31
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Document Transition Report	false
Securities Act File Number	1-07615
Entity Incorporation, State or Country Code	NV
Entity Tax Identification Number	74-1884980
Entity Address, Address Line One	55 Waugh Drive
Entity Address, Address Line Two	Suite 1000
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77007
City Area Code	713
Local Phone Number	435-1000
Title of 12(b) Security	Common Stock
Trading Symbol	KEX
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
ICFR Auditor Attestation Flag	true
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 4.5
Entity Common Stock, Shares Outstanding		58,522,000
Documents Incorporated by Reference [Text Block]	DOCUMENTS INCORPORATED BY REFERENCE Portions of the Company’s definitive proxy statement in connection with the Annual Meeting of Stockholders to be held April 26, 2024, to be filed with the Commission pursuant to Regulation 14A, and the related annual report for the fiscal year ended December 31, 2023, to be provided to the Company's stockholders pursuant to Rule 14a-3(b) are incorporated by reference into Parts II and III of this report.
Auditor Name	KPMG LLP
Auditor Location	Houston, TX
Auditor Firm ID	185
Document Financial Statement Error Correction [Flag]	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 32,577	$ 80,577
Accounts receivable:
Trade - less allowance for doubtful accounts of $7,636 ($7,684 in 2022)	526,691	483,406
Other	52,025	114,556
Inventories - net	454,389	461,848
Prepaid expenses and other current assets	69,479	71,372
Total current assets	1,135,161	1,211,759
Property and equipment - net	3,861,105	3,633,462
Operating lease right-of-use assets	152,216	154,507
Investment in affiliates	2,576	2,171
Goodwill	438,748	438,748
Other intangibles, net	42,927	51,463
Other assets	89,464	62,814
Total assets	5,722,197	5,554,924
Current liabilities:
Bank notes payable	8,068	3,292
Income taxes payable	1,486	323
Accounts payable	269,378	278,081
Accrued liabilities:
Interest	13,114	11,630
Insurance premiums and claims	84,825	65,088
Employee compensation	69,075	55,851
Taxes - other than on income	31,555	30,169
Other	30,377	42,014
Current portion of operating lease liabilities	33,340	36,444
Deferred revenues	134,577	119,305
Total current liabilities	675,795	642,197
Long-term debt, net - less current portion	1,008,527	1,076,326
Deferred income taxes	696,557	625,884
Operating lease liabilities - less current portion	138,811	142,140
Other long-term liabilities	15,830	23,209
Total long-term liabilities	1,859,725	1,867,559
Contingencies and commitments	0	0
Kirby stockholders' equity:
Common stock, $0.10 par value per share. Authorized 120,000,000 shares, issued 65,472,000	6,547	6,547
Additional paid-in capital	863,963	859,345
Accumulated other comprehensive income - net	35,006	16,853
Retained earnings	2,691,665	2,468,730
Treasury stock - at cost, 6,843,000 shares in 2023 and 5,565,000 shares in 2022	(411,750)	(308,598)
Total Kirby stockholders' equity	3,185,431	3,042,877
Noncontrolling interests	1,246	2,291
Total equity	3,186,677	3,045,168
Total liabilities and equity	$ 5,722,197	$ 5,554,924

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Assets, Current [Abstract]
Trade, allowance for doubtful accounts	$ 7,636	$ 7,684
Equity, Attributable to Parent [Abstract]
Common Stock, Par or Stated Value Per Share	$ 0.10	$ 0.10
Common Stock, Shares Authorized	120,000,000	120,000,000
Common Stock, Shares, Issued	65,472,000	65,472,000
Treasury Stock, Common, Shares	6,843,000	5,565,000

CONSOLIDATED STATEMENTS OF EARN

CONSOLIDATED STATEMENTS OF EARNINGS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues [Abstract]
Revenues	$ 3,091,640	$ 2,784,754	$ 2,246,660
Costs and expenses:
Costs of sales and operating expenses	2,180,422	2,060,941	1,652,961
Selling, General and Administrative Expense	335,213	302,692	266,911
Taxes, other than on income	34,766	35,071	36,251
Depreciation, Depletion and Amortization	211,156	201,443	213,718
Impairments and other charges	0	0	340,713
Gain on disposition of assets	(5,009)	(8,279)	(5,761)
Total costs and expenses	2,756,548	2,591,868	2,504,793
Operating income (loss)	335,092	192,886	(258,133)
Other income	11,041	16,677	10,001
Interest expense	(52,008)	(44,588)	(42,469)
Earnings (loss) before taxes on income	294,125	164,975	(290,601)
(Provision) benefit for taxes on income	(71,220)	(42,214)	43,830
Net earnings (loss)	222,905	122,761	(246,771)
Less: Net (earnings) loss attributable to noncontrolling interests	30	(470)	(183)
Net earnings (loss) attributable to Kirby	$ 222,935	$ 122,291	$ (246,954)
Net earnings (loss) per share attributable to Kirby common stockholders:
Earnings Per Share, Basic	$ 3.74	$ 2.04	$ (4.11)
Earnings Per Share, Diluted	$ 3.72	$ 2.03	$ (4.11)
Marine Transportation [Member]
Revenues [Abstract]
Revenues	$ 1,721,937	$ 1,616,967	$ 1,322,918
Distribution and Services [Member]
Revenues [Abstract]
Revenues	$ 1,369,703	$ 1,167,787	$ 923,742

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net earnings (loss)	$ 222,905	$ 122,761	$ (246,771)
Other comprehensive income , net of taxes:
Pension and postretirement benefits	16,728	43,868	36,547
Foreign currency translation adjustments	1,425	(1,049)	(1,061)
Total other comprehensive income , net of taxes	18,153	42,819	35,486
Total comprehensive income (loss), net of taxes	241,058	165,580	(211,285)
Net (earnings) loss attributable to noncontrolling interests	30	(470)	(183)
Comprehensive income (loss) attributable to Kirby	$ 241,088	$ 165,110	$ (211,468)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net earnings (loss)	$ 222,905	$ 122,761	$ (246,771)
Adjustments to reconcile net earnings (loss) to net cash provided by operations:
Depreciation and amortization	211,156	201,443	213,718
Provision (credit) for doubtful accounts	402	1,183	(138)
Provision (benefit) for deferred income taxes	65,298	37,782	(44,419)
Gain on disposition of assets	(5,009)	(8,279)	(5,761)
Impairments and other charges	0	0	340,713
Amortization of share-based compensation	14,941	13,865	15,713
Amortization of major maintenance costs	28,966	29,031	33,213
Other	(3,338)	(283)	(640)
Increase (decrease) in cash flows resulting from changes in:
Accounts receivable	(50,135)	(31,550)	29,126
Inventory	7,694	(127,095)	(19,248)
Other assets	(37,688)	(27,801)	(38,335)
Income taxes payable	71,604	1,975	480
Accounts payable	(18,271)	75,996	15,951
Accrued and other liabilities	31,703	5,100	27,974
Net cash provided by operating activities	540,228	294,128	321,576
Cash flows from investing activities:
Capital expenditures	(401,730)	(172,606)	(98,015)
Acquisitions of businesses and marine equipment, net of cash acquired	(37,500)	(3,900)	(9,115)
Proceeds from disposition of assets and other	26,081	36,905	51,342
Net cash used in investing activities	(413,149)	(139,601)	(55,788)
Cash flows from financing activities:
Borrowings (payments) on bank credit facilities, net	48,776	1,358	(248,105)
Borrowings on long-term debt	240,000	310,000	0
Payments on long-term debt	(350,000)	(395,000)	(60,000)
Payment of debt issue costs	(1,254)	(1,977)	0
Proceeds from exercise of stock options	4,209	3,887	629
Payments related to tax withholding for share-based compensation	(3,908)	(3,408)	(2,856)
Treasury stock purchases	(112,803)	(22,901)	0
Return of investment to noncontrolling interests and other	(99)	(722)	(981)
Net cash used in financing activities	(175,079)	(108,763)	(311,313)
Increase (decrease) in cash and cash equivalents	(48,000)	45,764	(45,525)
Cash and cash equivalents, beginning of year	80,577	34,813	80,338
Cash and cash equivalents, end of year	32,577	80,577	34,813
Cash paid (received) during the period:
Interest paid	49,317	42,816	40,878
Income taxes paid (refunded), net	(65,787)	2,553	(116,648)
Operating cash outflow from operating leases	43,954	44,229	44,089
Non-cash investing activity:
Capital expenditures included in accounts payable	9,567	2,996	18,633
Right-of-use assets obtained in exchange for lease obligations	$ 39,153	$ 22,799	$ 33,842

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]	Treasury Stock Common [Member]	Noncontrolling Interests [Member]
Beginning balance at Dec. 31, 2020	$ 3,087,553	$ 6,547	$ 844,979	$ (61,452)	$ 2,593,393	$ (299,161)	$ 3,247
Beginning balance (in shares) at Dec. 31, 2020		65,472,000				(5,434,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises	629		21			$ 608
Stock option exercises (in shares)						12,000
Issuance of stock for equity awards, net of forfeitures			(6,201)			$ 6,201
Issuance of stock for equity awards, net of forfeitures (in shares)						113,000
Tax withholdings on equity award vesting	(2,856)					$ (2,856)
Tax withholdings on equity award vesting (in shares)						(52,000)
Amortization of share-based compensation	15,713		15,713
Total comprehensive income (loss), net of taxes	(211,285)			35,486	(246,954)		183
Return of investment to noncontrolling interests	(972)						(972)
Ending balance at Dec. 31, 2021	2,888,782	$ 6,547	854,512	(25,966)	2,346,439	$ (295,208)	2,458
Ending balance (in shares) at Dec. 31, 2021		65,472,000				(5,361,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises	3,887		757			$ 3,130
Stock option exercises (in shares)						58,000
Issuance of stock for equity awards, net of forfeitures			(9,789)			$ 9,789
Issuance of stock for equity awards, net of forfeitures (in shares)						178,000
Tax withholdings on equity award vesting	(3,408)					$ (3,408)
Tax withholdings on equity award vesting (in shares)						(54,000)
Amortization of share-based compensation	13,865		13,865
Treasury stock purchases	(22,901)					$ (22,901)
Treasury stock purchases (in shares)						(386,000)
Total comprehensive income (loss), net of taxes	165,580			42,819	122,291		470
Return of investment to noncontrolling interests	(637)						(637)
Ending balance at Dec. 31, 2022	3,045,168	$ 6,547	859,345	16,853	2,468,730	$ (308,598)	2,291
Ending balance (in shares) at Dec. 31, 2022		65,472,000				(5,565,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises	4,208		453			$ 3,755
Stock option exercises (in shares)						71,000
Issuance of stock for equity awards, net of forfeitures			(10,776)			$ 10,776
Issuance of stock for equity awards, net of forfeitures (in shares)						194,000
Tax withholdings on equity award vesting	(3,908)					$ (3,908)
Tax withholdings on equity award vesting (in shares)						(58,000)
Amortization of share-based compensation	14,941		14,941
Treasury stock purchases	(112,803)					$ (112,803)
Treasury stock purchases (in shares)						(1,485,000)
Excise taxes on treasury stock purchases	(972)					$ (972)
Total comprehensive income (loss), net of taxes	241,058			18,153	222,935		(30)
Return of investment to noncontrolling interests	(1,015)						(1,015)
Ending balance at Dec. 31, 2023	$ 3,186,677	$ 6,547	$ 863,963	$ 35,006	$ 2,691,665	$ (411,750)	$ 1,246
Ending balance (in shares) at Dec. 31, 2023		65,472,000				(6,843,000)

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ 222,935	$ 122,291	$ (246,954)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2023
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. Such reclassifications have no impact on previously reported net earnings (loss), stockholders’ equity, or cash flows. 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-trade as of December 31, 2023 and 2022 wer e $ 136.3 million and $ 139.5 million, respectively, of accruals for revenues earned which have not been invoiced as of the end of each year. Accrued Insurance. The Company’s marine transportation and distribution and services operations are subject to hazards associated with such businesses. The marine transportation business in particular is subject to property damage and casualty risks associated with operating vessels carrying large volumes of bulk liquid and dry cargo in a marine environment. The Company maintains insurance coverage against these hazards with insurance companies subject to a deductible, below which the Company is liable. The Company uses historic experience and actuarial analysis by outside consultants to estimate an appropriate level of accrued insurance liabilities including estimates on individual claims outstanding and an estimated amount for losses that may have occurred but have not been reported to the Company (“IBNR”) or not yet fully developed. If the actual number of claims and magnitude were substantially greater than assumed, the required level of accrued liabilities for claims incurred but not reported or fully developed could be materially understated. Insurance premiums, IBNR losses and incurred claim losses, up to the Company’s deductible for the years ended December 31, 2023, 2022, and 2021, were $ 52.5 million , $ 39.1 million , and $ 37.8 million , respectively. The Company records receivables from its insurers for incurred claims above the Company’s deductible. If the solvency of the insurers becomes impaired, there could be an adverse impact on the accrued receivables and the availability of insurance. Included in accounts receivable-other as of December 31, 2023 and 2022 were $ 29.6 million and $ 27.7 million, 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, 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. Historically, credit risk with respect to these trade receivables has generally been considered minimal because of the financial strength of the Company’s customers; however, a United States or global recession or other adverse economic condition could impact the collectability of certain customers’ trade receivables which could have a material effect on the Company’s results of operations. Inventories. Inventories are stated at the lower of average cost or net realizable value. Property, Maintenance and Repairs. Property is recorded at cost or acquisition date fair value; improvements and betterments are capitalized as incurred. Depreciation is recorded using 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, improves the operating capacity, or replaces significant components of the vessel, which results in the costs being capitalized. The following table summarizes the balances of property and equipment – net (in thousands): December 31, 2023 2022 Land $ 39,567 $ 38,551 Marine transportation equipment 5,029,653 4,837,379 Buildings and other equipment 641,871 505,942 Construction in progress 112,947 70,271 $ 5,824,038 $ 5,452,143 Accumulated depreciation ( 1,962,933 ) ( 1,818,681 ) Property and equipment – net $ 3,861,105 $ 3,633,462 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, improve the operating capability, or replace significant components of the vessel are capitalized. The Company recognized amortization of major maintenance costs of $ 29.0 million , $ 29.0 million , and $ 33.2 million for the years ended December 31, 2023, 2022, and 2021, 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. For the years ended December 31, 2023, 2022 and 2021 , no interest was capitalized. Environmental Liabilities. The Company expenses costs related to environmental events as they are incurred or when a loss is considered probable and reasonably 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 tests at November 30, 2023, 2022, and 2021 . The Company also conducted an interim goodwill impairment test at September 30, 2021. Refer to Note 7, Impairments and other charges for more information. 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 a combination of projected discounted future operating cash flows using an appropriate discount rate and a market approach for comparable companies. The following table summarizes the changes in goodwill (in thousands): Marine Distribution and Total Balance at December 31, 2022 (gross) 505,784 560,155 1,065,939 Accumulated impairment and amortization ( 237,626 ) ( 389,565 ) ( 627,191 ) Balance at December 31, 2022 and 2023 $ 268,158 $ 170,590 $ 438,748 Other Intangibles. Other intangibles include assets for favorable contracts and customer relationships, distributorship and dealership agreements, trade names and non-compete agreements and liabilities for unfavorable leases and contracts. The following table summarizes the balances of other intangible assets and other intangible liabilities (in thousands): December 31, 2023 2022 Other intangible assets – gross $ 184,622 $ 203,242 Accumulated amortization ( 141,695 ) ( 151,779 ) Other intangible assets – net $ 42,927 $ 51,463 Other intangible liabilities – gross $ 8,800 $ 13,860 Accumulated amortization ( 8,800 ) ( 13,280 ) Other intangible liabilities – net $ — $ 580 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, 2023, 2022, and 2021, the amortization expense for intangibles was $ 8.1 million , $ 7.6 million , and $ 7.8 million , respectively. Estimated net amortization expense for amortizable intangible assets and liabilities for the next five years (2024 – 2028) is approximat ely $ 8.5 million, $ 8.5 million, $ 6.3 million, $ 5.0 million, and $ 3.5 million, respectively, and $ 11.1 million thereafter. As of December 31, 2023 , the weighted average amortization period for intangible assets and liabilities was approximately seven years . Revenue Recognition. The majority of marine transportation revenue is derived from term contracts, ranging from one to three years, some of which have renewal options, and the remainder is from spot contracts. The majority of the term contracts by revenue are for terms of one year. The Company provides marine transportation services for its customers and, in almost all cases, does not assume ownership of the products it transports. The Company enters into agreements with its customers to transport cargo from a designated origin to a designated destination at a set rate (affreightment) or at a daily rate (time charter). 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. Time charter or contracts of affreightment of one year or greater are considered term contract revenues and agreements of less than a year are included in spot contract revenues. Spot contracts typically involve an agreement with a customer to move cargo from a specific origin to a designated destination for a rate generally negotiated at the time the cargo movement takes place. Spot contract rates are typically 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. The performance of the service is invoiced as the transaction occurs and payment is required depending on each specific customer’s credit. Distribution products and services are generally sold based upon purchase orders or preferential service agreements with the customer that include fixed or determinable prices. Parts sales are recognized when control transfers to the customer, generally when title passes upon shipment to customers. Service revenue is recognized over time as the service is provided using measures of progress utilizing hours worked or costs incurred as a percentage of estimated hours or expected costs. Revenue from rental agreements is generally recognized on a straight-line basis over the rental period. The Company recognizes the revenues on manufacturing activities upon shipment and transfer of control to the customer. The transactions in the distribution and services segment (“KDS”) are typically invoiced as parts are shipped or upon the completion of the service job. Contract manufacturing activities are generally invoiced upon shipment and the Company will often get deposits from its customers prior to starting work, or progress payments during the project depending on the credit worthiness of the customer and the size of the project. 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 measured at fair value on the date of the grant and the cost for all grants made under the director plan and for grants made under the employee plan is generally recognized ratably over the vesting period of the restricted stock unit (“RSU”), stock option, or restricted stock. The employee plan, however, includes a provision for the continued vesting of unvested stock options and RSUs for employees who meet certain years of service and age requirements at the time of their retirement. The provision results in shorter expense accrual periods on stock options and RSUs granted to employees who are nearing retirement and meet the service and age requirements. Stock option grants are valued at the date of grant as calculated under the Black-Scholes option pricing model. The Company accounts for forfeitures as they occur. The Company’s stock-based compensation plans are more fully described in Note 8, 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. 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 performs an impairment assessment whenever events or changes in circumstances indicate that the carrying amount of long-lived 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 generally 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. If a triggering event is identified, the Company compares the carrying amount of the asset group to the estimated undiscounted future cash flows expected to result from the use of the asset group. If the carrying amount of the asset group exceeds the estimated undiscounted future cash flows, the Company measures the amount of the impairment by comparing the carrying amount of the asset group to its estimated fair value. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. 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. The fair value of the Company’s debt instruments is described in Note 5, Long-Term Debt. Accounting Standards In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures” (“ASU 2023-09”) which requires entities to disclose additional information in specified categories with respect to the reconciliation of the effective tax rate to the statutory rate for federal, state, and foreign income taxes. ASU 2023-09 is effective for annual and interim periods beginning after December 15, 2023, with early adoption permitted. The Company is currently evaluating the impact that the adoption of this standard will have on its consolidated financial statements. In November 2023, the FASB issued ASU No. 2023-07, “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures” (“ASU 2023-07”) to improve reportable segment disclosure requirements. The amendments require disclosure of significant segment expenses regularly provided to the chief operating decision maker (“CODM”) as well as other segment items, extend certain annual disclosures to interim periods, clarify the applicability to single reportable segment entities, permit more than one measure of profit or loss to be reported under certain conditions, and require disclosure of the title and position of the CODM. ASU 2023-07 is effective for annual periods beginning after December 15, 2024 and for interim periods beginning after December 15, 2025, with early adoption permitted. The Company is currently evaluating the impact that the adoption of this standard will have on its consolidated financial statements.

Acquisitions

Acquisitions	12 Months Ended
Acquisitions	Dec. 31, 2023
Business Combinations [Abstract]
Acquisitions	(2) Acquisitions On July 14, 2023, the Company purchased 23 inland tank barges with a total capacity of 265,000 barrels from an undisclosed seller for $ 37 million in cash. The 23 tank barges transport petrochemicals and refined products on the Mississippi River System and the Gulf Intracoastal Waterway. The average age of the 23 barges was 14 years. The Company purchased four inland tank barges from a leasing company for $ 0.5 million in cash during the 2023 third quarter. The Company had been leasing the barges prior to the purchase. On March 31, 2022, the Company paid $ 3.9 million in cash to purchase assets of a gearbox repair company in KDS. Assets acquired consisted primarily of property and equipment. The Company purchased four inland tank barges from a leasing company for $ 7.5 million in cash during 2021. The Company had been leasing the barges prior to the purchase. On October 4, 2021, the Company paid $ 1.6 million in cash to purchase assets of an energy storage systems manufacturer based in Texas which have been key to the development of new power generation solutions for electric fracturing equipment. Assets acquired and liabilities assumed consisted primarily of a right of use lease asset and lease liability for an operating lease assumed as part of the acquisition.

Revenues

Revenues	12 Months Ended
Revenues	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Revenues	(3) Revenues The following table sets forth the Company’s revenues by major source (in thousands): Year Ended December 31, 2023 2022 2021 Marine transportation segment: Inland transportation $ 1,416,483 $ 1,277,010 $ 1,005,145 Coastal transportation 305,454 339,957 317,773 $ 1,721,937 $ 1,616,967 $ 1,322,918 Distribution and services segment: Commercial and industrial $ 802,474 $ 651,566 $ 578,011 Oil and gas 567,229 516,221 345,731 $ 1,369,703 $ 1,167,787 $ 923,742 The Company’s revenue is measured based on consideration specified in its contracts with its customers. The Company recognizes revenue over time as it provides services to its customers, or at the point in time that control over a part or product transfers to its customer. Contract Assets and Liabilities . Contract liabilities represent advance consideration received from customers, and are recognized as revenue over time or at a point in time as the related performance obligation is satisfied. Revenues recognized during the years ended December 31, 2023, 2022, and 2021, that were included in the opening contract liability balances wer e $ 84.0 million, $ 61.7 million and $ 40.9 million , respectively. The Company has recognized all contract liabilities within the deferred revenues financial statement caption on the balance sheet. The Company did no t have any contract assets at December 31, 2023 or December 31, 2022. The Company applies the practical expedient that allows non-disclosure of information about remaining performance obligations that have original expected durations of one year or less.

Segment Data

Segment Data	12 Months Ended
Segment Data	Dec. 31, 2023
Segment Reporting [Abstract]
Segment Data	(4) Segment Data The Company’s operations are aggregated into two reportable business segments as follows: Marine Transportation — Provides marine transportation by United States flagged vessels principally of liquid cargoes throughout the United States inland waterway system, along all three United States coasts, 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 genuine replacement parts for engines, transmissions, reduction gears and related equipment used in oilfield services, marine, power generation, on-highway, and other industrial applications. The Company also rents equipment including generators, industrial compressors, high capacity lift trucks, and refrigeration trailers for use in a variety of industrial markets, and manufactures and remanufactures oilfield service equipment, including pressure pumping units, electric power generation equipment, specialized electrical distribution and control equipment, and high capacity energy storage/battery systems for oilfield service and railroad customers. 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 KDS from KMT of $ 39.8 million , $ 31.9 million , and $ 23.6 million in 2023, 2022, and 2021, respectively, as well as the related intersegment profit of $ 4.0 million , $ 3.2 million , and $ 2.4 million in 2023, 2022, and 2021, respectively, have been eliminated from the tables below. The following tables set 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 (in thousands): Year Ended December 31, 2023 2022 2021 Revenues: Marine transportation $ 1,721,937 $ 1,616,967 $ 1,322,918 Distribution and services 1,369,703 1,167,787 923,742 $ 3,091,640 $ 2,784,754 $ 2,246,660 Segment profit (loss): Marine transportation $ 238,943 $ 136,184 $ 63,015 Distribution and services 114,481 67,037 27,607 Other ( 59,299 ) ( 38,246 ) ( 381,223 ) $ 294,125 $ 164,975 $ ( 290,601 ) Depreciation and amortization: Marine transportation $ 184,225 $ 177,551 $ 185,979 Distribution and services 19,842 16,776 20,573 Other 7,089 7,116 7,166 $ 211,156 $ 201,443 $ 213,718 Capital expenditures: Marine transportation $ 255,411 $ 147,170 $ 84,353 Distribution and services 140,769 21,713 8,104 Other 5,550 3,723 5,558 $ 401,730 $ 172,606 $ 98,015 December 31, 2023 2022 Total assets: Marine transportation $ 4,454,931 $ 4,285,647 Distribution and services 1,156,384 1,041,841 Other 110,882 227,436 $ 5,722,197 $ 5,554,924 The following table presents the details of “Other” segment profit (loss) (in thousands): Year Ended December 31, 2023 2022 2021 General corporate expenses $ ( 23,341 ) $ ( 18,614 ) $ ( 13,803 ) Gain on disposition of assets 5,009 8,279 5,761 Impairments and other charges — — ( 340,713 ) Interest expense ( 52,008 ) ( 44,588 ) ( 42,469 ) Other income 11,041 16,677 10,001 $ ( 59,299 ) $ ( 38,246 ) $ ( 381,223 ) The following table presents the details of “Other” total assets (in thousands): December 31, 2023 2022 General corporate assets $ 108,306 $ 225,265 Investment in affiliates 2,576 2,171 $ 110,882 $ 227,436

Long-Term Debt

Long-Term Debt	12 Months Ended
Long-Term Debt	Dec. 31, 2023
Debt Disclosure [Abstract]
Long-Term Debt	(5) Long-Term Debt The following table presents the carrying value and fair value (determined using inputs characteristic of a Level 2 fair value measurement) of debt outstanding (in thousands): December 31, 2023 2022 Carrying Value Fair Value Carrying Value Fair Value Revolving Credit Facility due July 29, 2027 (a) $ 44,000 $ 44,000 $ — $ — Term Loan due July 29, 2027 (a) 170,000 170,000 170,000 170,000 3.29 % senior notes due February 27, 2023 — — 350,000 352,275 4.2 % senior notes due March 1, 2028 500,000 475,920 500,000 477,660 3.46 % senior notes due January 19, 2033 60,000 49,955 60,000 42,647 3.51 % senior notes due January 19, 2033 240,000 200,698 — — Credit Line due June 30, 2024 — — — — Bank notes payable 8,068 8,068 3,292 3,292 1,022,068 948,641 1,083,292 1,045,874 Unamortized debt discounts and issuance costs (b) ( 5,473 ) — ( 3,674 ) — $ 1,016,595 $ 948,641 $ 1,079,618 $ 1,045,874 (a) Variable interest rate of 6.8 % and 5.8 % at December 31, 2023 and 2022, respectively. (b) Excludes $ 1.8 million attributable to the 2027 Revolving Credit Facility included in other assets at December 31, 2022 . The aggregate payments due on the long-term debt in each of the next five years were as follows (in thousands): 2024 $ 8,068 2025 32,500 2026 56,250 2027 125,250 2028 500,000 Thereafter 300,000 $ 1,022,068 At the beginning of 2022, the Company had an amended and restated credit agreement (the “2024 Credit Agreement”) with a group of commercial banks, with JPMorgan Chase Bank, N.A. as the administrative agent bank, that allowed for an $ 850 million unsecured revolving credit facility (the “2024 Revolving Credit Facility”) and an unsecured term loan (the “2024 Term Loan”) with a maturity date of March 27, 2024 . The 2024 Term Loan was prepayable, in whole or in part, without penalty. On July 29, 2022, the Company entered into a new credit agreement (the “2027 Credit Agreement”) with a group of commercial banks, with JPMorgan Chase Bank, N.A. as the administrative agent bank that allows for a $ 500 million unsecured revolving credit facility (the “2027 Revolving Credit Facility”) and a $ 250 million unsecured term loan (the “2027 Term Loan”) with a maturity date of July 29, 2027 . The 2027 Credit Agreement replaced the 2024 Credit Agreement. In conjunction with entering into the 2027 Credit Agreement, on July 29, 2022, the Company borrowed $ 35 million under the 2027 Revolving Credit Facility and $ 250 million under the 2027 Term Loan to repay borrowings under the 2024 Term Loan. In the fourth quarter of 2022, the Company repaid $ 80.0 million under the 2027 Term Loan prior to scheduled maturities. As a result, no repayments are required until June 30, 2025. Outstanding letters of credit under the 2027 Revolving Credit Facility were $ 6,000 and available borrowing capacity was $ 456.0 million as of December 31, 2023. The 2027 Term Loan is repayable in quarterly installments, with no repayments until June 30, 2025, in increasing percentages of the original principal amount of the loan, with the remaining unpaid balance of approximately $ 43.8 million payable upon maturity, assuming no prepayment. The 2027 Term Loan is prepayable, in whole or in part, without penalty. The 2027 Credit Agreement provides for a variable interest rate based on the Secured Overnight Financing Rate (“SOFR”) or a base rate calculated with reference to the prime rate quoted by The Wall Street Journal, the Federal Reserve Bank of New York Rate plus 0.5 %, or the adjusted SOFR rate for a one month interest period plus 1.0 %, among other factors (the “Alternate Base Rate”). The interest rate varies with the Company’s credit rating and is currently 137.5 basis points over SOFR or 37.5 basis points over the Alternate Base Rate. The 2027 Credit Agreement contains certain financial covenants including an interest coverage ratio and debt-to-capitalization ratio. In addition to financial covenants, the 2027 Credit Agreement 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. The 2027 Credit Agreement specifies certain events of default, upon the occurrence of which the maturity of the outstanding loans may be accelerated, including the failure to pay principal or interest, violation of covenants and default on other indebtedness, among other events. Borrowings under the 2027 Credit Agreement may be used for general corporate purposes including acquisitions. The 2027 Revolving Credit Facility includes a $ 25 million commitment which may be used for standby letters of credit. The Company has $ 500 million of 4.2 % senior unsecured notes due March 1, 2028 (the “2028 Notes”) with U.S. Bank National Association, as trustee. No principal payments are required until maturity. Interest payments of $ 10.5 million are due semi-annually on March 1 and September 1 of each year. The 2028 Notes are unsecured and rank equally in right of payment with the Company’s other unsecured senior indebtedness. The 2028 Notes contain certain covenants on the part of the Company, including covenants relating to liens, sale-leasebacks, asset sales and mergers, among others. The 2028 Notes 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. On February 3, 2022, the Company entered into a note purchase agreement for the issuance of $ 300 million of unsecured senior notes with a group of institutional investors, consisting of $ 60 million of 3.46 % series A notes (“Series A Notes”) and $ 240 million of 3.51 % series B notes (“Series B Notes”), each due January 19, 2033 (collectively, the “2033 Notes”). The Series A Notes were issued on October 20, 2022, and the Series B Notes were issued on January 19, 2023. No principal payments will be required until maturity. Beginning in 2023, interest payments of $ 5.3 million are due semi-annually on January 19 and July 19 of each year, with the exception of the first payment on January 19, 2023, which was $ 0.5 million. The 2033 Notes are unsecured and rank equally in right of payment with the Company ’ s other unsecured senior indebtedness. The 2033 Notes 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 2033 Notes 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. The 3.29 % unsecured senior notes due February 27, 2023 (the “2023 Notes”) were repaid using a combination of the proceeds from the issuance of the 2033 Notes and availability under the 2027 Revolving Credit Facility. The Company has a $ 10.0 million 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, 2024 . 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 of December 31, 2023. Outstanding letters of credit under the Credit Line were $ 7.3 million and available borrowing capacity was $ 2.7 million as of December 31, 2023. The Company also had $ 8.1 million and $ 3.3 million of short-term unsecured loans outstanding, as of December 31, 2023 and 2022, respectively, related to its Colombia operations. As of December 31, 2023 , the Company was in compliance with all covenants under its debt instruments.

Leases

Leases	12 Months Ended
Leases	Dec. 31, 2023
Leases [Abstract]
Leases	(6) Leases The Company currently leases various facilities and equipment under cancelable and noncancelable operating leases. The accounting for the Company’s leases may require judgments, which include determining whether a contract contains a lease, allocating the consideration between lease and non-lease components, and determining the incremental borrowing rates. Leases with an initial noncancelable term of 12 months or less are not recorded on the balance sheet and the related lease expense is recognized on a straight-line basis over the lease term. The Company has also elected to combine lease and non-lease components on all classes of leased assets, except for leased towing vessels for which the Company estimat es approximately 70 % of the costs relate to service costs and other non-lease components. Variable lease costs relate primarily to real estate executory costs (i.e. taxes, insurance and maintenance). Future minimum lease payments under operating leases that have initial noncancelable lease terms in excess of one year were as follows (in thousands): 2024 $ 38,943 2025 27,638 2026 24,945 2027 22,842 2028 18,318 Thereafter 79,755 Total lease payments 212,441 Less: imputed interest ( 40,290 ) Operating lease liabilities $ 172,151 The following table summarizes lease costs (in thousands): Year Ended December 31, 2023 2022 2021 Operating lease cost $ 42,821 $ 42,319 $ 40,786 Variable lease cost 2,376 1,780 1,793 Short-term lease cost 30,005 25,365 17,914 Sublease income ( 3,223 ) ( 305 ) ( 1,032 ) Total lease cost $ 71,979 $ 69,159 $ 59,461 The following table summarizes other supplemental information about the Company’s operating leases: December 31, 2023 2022 2021 Weighted average discount rate 4.4 % 4.1 % 3.8 % Weighted average remaining lease term 9 years 9 years 9 years

Impairments and Other Charges

Impairments and Other Charges	12 Months Ended
Impairments and Other Charges	Dec. 31, 2023
Asset Impairment Charges [Abstract]
Impairments and Other Charges	(7) Impairments and Other Charges During the third quarter of 2021, the Company decided to exit the Hawaii marine transportation market, selling marine transportation equipment including four coastal tank barges, seven coastal tugboats, and certain other assets for aggregate cash proceeds of $ 17.2 million. In addition, as of September 30, 2021, the Company retired and classified as held for sale, an additional 12 coastal tank barges and four coastal tugboats which were underutilized. The sales and retirements of coastal marine transportation equipment resulted in an aggregate non‑cash impairment charge of $ 97.5 million to reduce the carrying value of these assets to their estimated sales prices, net of costs to sell. As a result of the sale of the Hawaii marine transportation equipment, and the decision to retire certain additional underutilized coastal tank barges and tugboats, the Company concluded that a triggering event had occurred and performed interim quantitative impairment tests as of September 30, 2021 for certain of KMT’s long-lived assets and goodwill within the coastal marine market. The Company determined the estimated fair value of such long-lived assets using a combination of a cost approach, a discounted cash flow analysis, and a market approach. The Company determined the estimated fair value of the reporting unit using a combination of a discounted cash flow analysis and a market approach for comparable companies. These analyses included management’s judgment regarding short-term and long-term internal forecasts, updated for recent events, appropriate discount rates, and capital expenditures using inputs characteristic of a Level 3 fair value measurement. In performing the impairment test of certain long-lived assets within KMT, the Company determined that the carrying value of certain long-lived assets, including certain coastal marine transportation equipment and operating lease right-of-use assets, were no longer recoverable, resulting in a non-cash impairment charge of $ 24.2 million during the three months ended September 30, 2021 to reduce such long-lived assets to fair value. Based upon the results of the goodwill impairment test, the Company concluded that the carrying value of one reporting unit in KMT exceeded its estimated fair value. The carrying value of the reporting unit, including goodwill, and after recording impairments of long-lived assets identified above, exceeded its estimated fair value, resulting in a non-cash goodwill impairment charge of $ 219.1 million for the three months ended September 30, 2021.

Stock Award Plans

Stock Award Plans	12 Months Ended
Stock Award Plans	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Stock Award Plans	(8) 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 were as follows (in thousands): Year Ended December 31, 2023 2022 2021 Compensation cost $ 14,941 $ 13,865 $ 15,713 Income tax benefit $ 3,616 $ 3,533 $ 4,410 The Company has an employee stock award plan for selected officers and other key employees which provides for the issuance of RSUs, stock options, restricted stock awards, and performance awards. Restricted stock and RSUs generally vest ratably over five years , however, the plan includes a provision for the continued vesting of unvested stock options and RSUs for employees who meet certain years of service and age requirements at the time of their retirement. The provision results in shorter expense accrual periods on stock options and RSUs granted to employees who are nearing retirement and meet the service and age requirements. At December 31, 2023, there we re 2,045,694 sh ares available for future grants under the Plan. 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 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: Outstanding Weighted Outstanding at December 31, 2022 396,165 $ 70.06 Exercised ( 117,896 ) $ 60.84 Expired ( 23,024 ) $ 73.66 Outstanding at December 31, 2023 255,245 $ 74.00 The following table summarizes information about the Company’s outstanding and exercisable stock options under the employee plan at December 31, 2023: Options Outstanding Options Exercisable Range of Exercise Number Weighted Weighted Aggregated Number Weighted Aggregated $ 64.89 15,500 1.3 $ 64.89 15,500 $ 64.89 $ 73.29 – $ 75.50 233,040 2.1 $ 74.29 233,040 $ 74.29 $ 84.90 6,705 2.3 $ 84.90 6,705 $ 84.90 $ 64.89 – $ 84.90 255,245 2.0 $ 74.00 $ 1,187 255,245 $ 74.00 $ 1,187 There were no unvested restricted stock awards under the employee plan at December 31, 2023 and 2022 and no restricted stock awards were granted under the employee plan during 2023, 2022, and 2021. The following is a summary of RSU activity under the employee plan described above: Unvested RSUs Weighted Nonvested balance at December 31, 2022 558,819 $ 62.13 Granted 184,440 $ 72.23 Vested ( 161,550 ) $ 64.85 Forfeited ( 27,105 ) $ 63.68 Nonvested balance at December 31, 2023 554,604 $ 64.61 The weighted average grant date fair value of RSUs granted for the years ended December 31, 2023, 2022, and 2021 was $ 72.23 , $ 66.13 , and $ 51.36 , respectively. During February 2024, the Company gra nted 164,793 RSUs to selected officers and other key employees under its employee stock award plan, which substantially all vest ratably over five yea rs . 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, 2023 , 369,360 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: Outstanding Weighted Outstanding at December 31, 2022 56,480 $ 86.19 Granted 3,865 $ 72.83 Exercised — $ — Expired ( 30,000 ) $ 80.04 Outstanding at December 31, 2023 30,345 $ 90.57 The following table summarizes information about the Company’s outstanding and exercisable stock options under the director plan at December 31, 2023: Options Outstanding Options Exercisable Range of Exercise Number Weighted Weighted Aggregate Number Weighted Aggregate $ 70.65 – $ 73.57 7,053 6.6 $ 71.85 6,278 $ 71.75 $ 84.90 – $ 85.30 5,292 4.8 $ 85.10 5,292 $ 85.10 $ 99.52 18,000 0.3 $ 99.52 18,000 $ 99.52 $ 70.65 – $ 99.52 30,345 2.6 $ 90.57 $ 47 29,570 $ 91.04 $ 42 The following is a summary of the restricted stock award activity under the director plan described above: Unvested Weighted Nonvested balance at December 31, 2022 1,698 $ 65.36 Granted 31,526 $ 72.67 Vested ( 32,604 ) $ 72.29 Nonvested balance at December 31, 2023 620 $ 72.65 The weighted average grant date fair value of restricted stock awards granted under the director plan for the years ended December 31, 2023, 2022, and 2021 were $ 72.67 , $ 64.61 , and $ 65.13 , respectively. The total intrinsic value of all stock options exercised under all of the Company’s plans wa s $ 1.5 million, $ 0.4 million , and $ 0.1 million for the years ended December 31, 2023, 2022, and 2021, respectively. The total fair value of all the restricted stock vestings under all of the Company’s plans was $ 2.5 million, $ 3.2 million, and $ 5.3 million for the years ended December 31, 2023, 2022, and 2021 , respectively. The actual tax benefit realized for tax deductions from restricted stock vestings was $ 0.6 million, $ 0.8 million, and $ 1.5 million for the years ended December 31, 2023, 2022, and 2021, respectively. The total fair value of all the RSU vestings under the Company’s employee plan was $ 10.9 million, $ 9.5 million, and $ 4.4 million for the years ended December 31, 2023, 2022, and 2021 , respectively. The actual tax benefit realized for tax deductions from RSU vestings was $ 2.6 million, $ 2.4 million, and $ 1.2 million for the years ended December 31, 2023, 2022, and 2021, respectively. As of December 31, 2023 , there was $ 45,000 of unrecognized compensation cost related to restricted stock and $ 15.3 million relate d to nonvested RSUs. The restricted stock is expected to be recognized over a weighted average period of approximately 0.2 years and RSUs over approximately 2.7 years. There were no stock options granted under the employee plan during the years ended December 31, 2023, 2022, and 2021. T he weighted average per share fair value of stock options granted under the director plan during the year ended December 31, 2023 was $ 32.33 and the f air value of the stock options was $ 0.1 million . There were no stock options granted under the director plan during the years ended December 31, 2022 and 2021. The Company currently uses treasury stock shares for restricted stock grants, RSU vestings, 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 granted were as follows: Year Ended December 31, 2023 Dividend yield None Average risk-free interest rate 3.7 % Stock price volatility 35 % Estimated option term 7 years

Taxes on Income

Taxes on Income	12 Months Ended
Taxes on Income	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Taxes on Income	(9) Taxes on Income Earnings (loss) before taxes on income and details of the provision (benefit) for taxes on income were as follows (in thousands): Year Ended December 31, 2023 2022 2021 Earnings (loss) before taxes on income: United States $ 293,011 $ 164,590 $ ( 290,181 ) Foreign 1,114 385 ( 420 ) $ 294,125 $ 164,975 $ ( 290,601 ) Provision (benefit) for taxes on income: U.S. Federal: Current $ ( 41 ) $ 513 $ ( 460 ) Deferred 61,205 34,980 ( 48,843 ) $ 61,164 $ 35,493 $ ( 49,303 ) U.S. State: Current $ 5,498 $ 3,793 $ 1,560 Deferred 4,093 2,802 4,424 $ 9,591 $ 6,595 $ 5,984 Foreign: Current $ 465 $ 126 $ ( 511 ) $ 465 $ 126 $ ( 511 ) Consolidated: Current $ 5,922 $ 4,432 $ 589 Deferred 65,298 37,782 ( 44,419 ) $ 71,220 $ 42,214 $ ( 43,830 ) On November 13, 2021, the voters of the state of Louisiana approved a constitutional amendment that removed the corporate tax deduction for federal income taxes paid and lowered the corporate income tax rate from 8 % to 7.5 % effective January 1, 2022. The result of the amendment was an increase in the effective Louisiana state income tax rate, net of deduction for federal income tax, from 6.3 % to 7.5 %. As a result of the amendment, the Company recognized a one-time deferred tax provisi on of $ 5.7 million durin g the fourth quarter of 2021 due to remeasuring the Company’s Louisiana and U.S. deferred tax assets and liabilities based on the new effective Louisiana state income tax rate. During 2021, the Company received a tax refund of $ 119.5 million, including accrued interest, for its 2019 tax return related to net operating losses being carried back to offset taxable income generated between 2014 and 2017. At December 31, 2022, the Company had a federal income tax receivable of $ 70.4 million, included in Accounts Receivable – Other on the balance sheet. In April 2023, the Company received its tax refund of $ 70.4 million plus accrued interest. The Company’s provision (benefit) for taxes on income varied from the statutory federal income tax rate due to the following: Year Ended December 31, 2023 2022 2021 United States income tax statutory rate 21.0 % 21.0 % 21.0 % State and local taxes, net of federal benefit 2.6 3.1 ( 1.7 ) Other – net 0.6 1.5 ( 4.2 ) 24.2 % 25.6 % 15.1 % The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and liabilities were as follows (in thousands): December 31, 2023 2022 Deferred tax assets: Allowance for doubtful accounts $ 1,549 $ 1,556 Inventory 10,500 11,679 Insurance accruals 6,077 4,856 Deferred compensation 11,441 7,703 Unrealized gain on defined benefit plans ( 9,982 ) ( 5,532 ) Goodwill and other intangibles 39,719 52,847 Operating loss carryforwards 52,082 79,699 Retirement benefits 3,548 5,472 Other 13,467 9,962 128,401 168,242 Valuation allowances ( 22,073 ) ( 19,960 ) 106,328 148,282 Deferred tax liabilities: Property ( 695,233 ) ( 671,830 ) Deferred state taxes ( 90,457 ) ( 87,445 ) Other ( 17,195 ) ( 14,891 ) ( 802,885 ) ( 774,166 ) $ ( 696,557 ) $ ( 625,884 ) During 2023, the Company generated federal taxable income which was completely offset by federal net operating loss carryforwards. The Company had federal operating loss deferred tax assets of $ 19.8 million and $ 47.9 million at December 31, 2023 and 2022, respectively. The Company had state operating loss deferred tax assets of $ 27.2 million and $ 26.6 million at December 31, 2023 and 2022, respectively. The valuation allowance for state deferred tax assets as of December 31, 2023 and 2022 was $ 17.0 million a nd $ 14.8 million , 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 2030 and none will expire in fiscal 2024. As of December 31, 2023 and 2022, the Company had a Canadian net operating loss carryforward of $ 5.1 million which expires between 2037 and 2043 . 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. During the first quarter of 2023, the Internal Revenue Service (“IRS”) communicated to the Company that it had completed its examination of the Company’s federal income tax returns for the years 2013 through 2020 . With few exceptions, the Company and its subsidiaries’ state income tax returns are open to audit under the statute of limitations for the 2017 through 2022 tax years . As of December 31, 2023, the Company has provided a liability of $ 0.8 million 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 $ 0.7 million, with the difference between the total amount of u nrecognized 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, 2024 due to the uncertainty of possible examination results. A reconciliation of the beginning and ending amount of the liability for unrecognized tax benefits is as follows (in thousands): Year Ended December 31, 2023 2022 2021 Balance at beginning of year $ 662 $ 737 $ 783 Additions based on tax positions related to the current year — 13 13 Additions for tax positions of prior years — 66 281 Reductions for tax positions of prior years ( 14 ) ( 154 ) ( 340 ) Balance at end of year $ 648 $ 662 $ 737 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 had $ 0.2 million of accrued liabilities for the payment of interest and penalties at both December 31, 2023 and 2022.

Earnings Per Share

Earnings Per Share	12 Months Ended
Earnings Per Share	Dec. 31, 2023
Earnings Per Share [Abstract]
Earnings Per Share	(10) Earnings Per Share The following table presents the components of basic and diluted earnings (loss) per share (in thousands, except per share amounts): Year Ended December 31, 2023 2022 2021 Net earnings (loss) attributable to Kirby $ 222,935 $ 122,291 $ ( 246,954 ) Undistributed earnings allocated to restricted shares ( 62 ) ( 33 ) — Earnings (loss) available to Kirby common stockholders — basic 222,873 122,258 ( 246,954 ) Undistributed earnings allocated to restricted shares 62 33 — Undistributed earnings reallocated to restricted shares ( 62 ) ( 33 ) — Earnings (loss) available to Kirby common stockholders — diluted $ 222,873 $ 122,258 $ ( 246,954 ) Shares outstanding: Weighted average common stock issued and outstanding 59,548 60,055 60,099 Weighted average unvested restricted stock ( 17 ) ( 17 ) ( 46 ) Weighted average common stock outstanding — basic 59,531 60,038 60,053 Dilutive effect of stock options and restricted stock units 326 291 — Weighted average common stock outstanding — diluted 59,857 60,329 60,053 Net earnings (loss) per share attributable to Kirby common stockholders: Basic $ 3.74 $ 2.04 $ ( 4.11 ) Diluted $ 3.72 $ 2.03 $ ( 4.11 ) Diluted earnings per share was computed using the treasury stock method. Certain outstanding options to purchase approximately 33,000 , 381,000 , and 567,000 shares of common stock were excluded in the computation of diluted earnings per share as of December 31, 2023, 2022, and 2021 , respectively, as such stock options would have been antidilutive. Certain outstanding RSUs to convert to 7,000 shares of common stock were also excluded in the computation of diluted earnings per share as of December 31, 2021 as such RSUs would have been antidilutive. No RSUs were antidilutive at December 31, 2023 and 2022.

Inventories

Inventories	12 Months Ended
Inventories	Dec. 31, 2023
Inventory Disclosure [Abstract]
Inventories	(11) Inventories The following table presents the details of inventories — net (in thousands): December 31, 2023 2022 Finished goods $ 351,050 $ 358,702 Work in process 103,339 103,146 $ 454,389 $ 461,848

Retirement Plans

Retirement Plans	12 Months Ended
Retirement Plans	Dec. 31, 2023
Retirement Benefits [Abstract]
Retirement Plans	(12) Retirement Plans The Company sponsors a defined benefit plan (the “Kirby Pension 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 the Kirby 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. On February 14, 2018, with the acquisition of Higman Marine, Inc. (“Higman”), the Company assumed Higman’s pension plan (the “Higman Pension Plan”) for its inland vessel personnel and office staff. On March 27, 2018, the Company amended the Higman Pension Plan to close it to all new entrants and cease all benefit accruals for periods after May 15, 2018 for all participants. The Company made contributions to the Higman Pension Plan of $ 8.2 million, $ 0.9 million and $ 0.5 million for the years ended December 31, 2023, 2022 and 2021, respectively. The aggregate fair value of plan assets of the Company’s pension plans was $ 375.9 million and $ 341.1 million at December 31, 2023 and 2022, respectively. Pension assets were allocated among asset categories as follows: December 31, Current Asset Category 2023 2022 Allocation Policy U.S. equity securities 51 % 50 % 45 % — 50 % — 55 % International equity securities 20 20 12 % — 20 % — 28 % Debt securities 29 30 20 % — 30 % — 40 % Cash and cash equivalents — — 0 % — 0 % — 0 % 100 % 100 % At December 31, 2022 , $ 4.8 million was held in cash as well as debt and equity securities classified within Level 1 of the valuation hierarchy. There were no investments within Level 3 of the valuation hierarchy at December 31, 2023 and 2022. All other plan assets are invested in common collective trusts and valued using the net asset value per share practical expedient and therefore not valued within the valuation hierarchy. 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 investing in asset classes offering sufficient liquidity and trading 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 retur n of 6.75 % in both 2023 and 2022. 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 115 % of the pension plans’ accumulated benefit obligation at December 31, 2023, including both the Kirby Pension Plan and the Higman Pension Plan. 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): Pension Benefits Other Postretirement Benefits Pension Plans SERP Postretirement Welfare Plan 2023 2022 2023 2022 2023 2022 Change in benefit obligation Benefit obligation at beginning of year $ 339,509 $ 495,272 $ 833 $ 1,033 $ 432 $ 582 Service cost 3,695 6,538 — — — — Interest cost 18,356 14,779 43 29 22 17 Actuarial (gain) loss 13,241 ( 158,816 ) 91 ( 74 ) 65 ( 58 ) Gross benefits paid ( 32,052 ) ( 12,665 ) ( 153 ) ( 155 ) ( 104 ) ( 109 ) Settlements — ( 5,599 ) — — — — Benefit obligation at end of year $ 342,749 $ 339,509 $ 814 $ 833 $ 415 $ 432 Accumulated benefit obligation at end of year $ 326,987 $ 325,274 $ 814 $ 833 $ 415 $ 432 Weighted-average assumption used to determine benefit obligation at end of year Discount rate (a) 5.1 %/ 5.2 % 5.5 % 5.1 % 5.5 % 5.1 % 5.5 % Rate of compensation increase Service-based table Service-based table — — — — Health care cost trend rate Initial rate — — — — 6.25 % 6.50 % Ultimate rate — — — — 5.0 % 5.0 % Years to ultimate — — — — 2029 2029 Change in plan assets Fair value of plan assets at beginning of year $ 341,061 $ 430,821 $ — $ — $ — $ — Actual return on plan assets 58,734 ( 72,402 ) — — — — Employer contribution 8,174 906 153 155 104 109 Gross benefits paid ( 32,052 ) ( 12,665 ) ( 153 ) ( 155 ) ( 104 ) ( 109 ) Settlements — ( 5,599 ) — — — — Fair value of plan assets at end of year $ 375,917 $ 341,061 $ — $ — $ — $ — (a) The 2023 discount rate was 5.1 % for the Kirby Pension Plan and 5.2 % for the Higman Pension Plan. The 2022 discount rate was 5.5 % for both the Kirby Pension Plan and the Higman Pension Plan. During the year ending December 31, 2023, actual returns on plan assets performed better than expected which improved the funding position. During the year ending December 31, 2022, actual returns on plan assets performed less than expected which deteriorated the funding position but the overall funded position at December 31, 2022 was improved due to a decrease in the benefit obligation primarily due to an increase in the discount rate. 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 (in thousands): Pension Benefits Other Postretirement Benefits Pension Plans SERP Postretirement Welfare Plan 2023 2022 2023 2022 2023 2022 Funded status at end of year Fair value of plan assets $ 375,917 $ 341,061 $ — $ — $ — $ — Benefit obligations ( 342,749 ) ( 339,509 ) ( 814 ) ( 833 ) ( 415 ) ( 432 ) Funded status and amount recognized at end of year $ 33,168 $ 1,552 $ ( 814 ) $ ( 833 ) $ ( 415 ) $ ( 432 ) Amounts recognized in the consolidated balance sheets Noncurrent asset 42,698 18,695 — — — — Current liability — — ( 106 ) ( 106 ) ( 46 ) ( 49 ) Long-term liability ( 9,530 ) ( 17,143 ) ( 708 ) ( 727 ) ( 369 ) ( 383 ) Amounts recognized in accumulated other comprehensive income Net actuarial (gain) loss $ ( 48,033 ) $ ( 25,449 ) $ 391 $ 324 $ ( 1,890 ) $ ( 2,299 ) Prior service cost (credit) — — — — — — Accumulated other compensation income $ ( 48,033 ) $ ( 25,449 ) $ 391 $ 324 $ ( 1,890 ) $ ( 2,299 ) The following table presents the expected cash flows for the Company’s defined benefit plans and postretirement benefit plan (in thousands): Pension Benefits Other Postretirement Benefits Pension Plans SERP Postretirement Welfare Plan 2023 2022 2023 2022 2023 2022 Expected employer contributions First year $ 1,770 $ 8,374 $ — $ — $ — $ — Expected benefit payments (gross) Year one $ 16,696 $ 16,312 $ 108 $ 108 $ 47 $ 50 Year two 17,513 16,899 103 104 46 49 Year three 18,169 17,808 98 99 44 47 Year four 19,096 18,650 93 94 43 45 Year five 19,860 19,707 88 90 41 43 Next five years 108,717 110,417 337 359 167 176 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 were as follows (in thousands): Pension Benefits Pension Plans SERP 2023 2022 2021 2023 2022 2021 Components of net periodic benefit cost Service cost $ 3,695 $ 6,538 $ 7,961 $ — $ — $ — Interest cost 18,356 14,779 14,239 43 29 31 Expected return on plan assets ( 22,910 ) ( 28,399 ) ( 26,244 ) — — — Amortization of actuarial loss — 34 4,193 23 30 40 Net periodic benefit cost ( 859 ) ( 7,048 ) 149 66 59 71 Other changes in plan assets and benefit obligations recognized in other comprehensive income Current year actuarial (gain) loss ( 22,583 ) ( 58,015 ) ( 44,583 ) 91 ( 74 ) ( 12 ) Recognition of actuarial loss — ( 34 ) ( 4,193 ) ( 23 ) ( 30 ) ( 40 ) Total recognized in other comprehensive income ( 22,583 ) ( 58,049 ) ( 48,776 ) 68 ( 104 ) ( 52 ) Total recognized in net periodic benefit cost and other comprehensive income $ ( 23,442 ) $ ( 65,097 ) $ ( 48,627 ) $ 134 $ ( 45 ) $ 19 Weighted average assumptions used to determine net periodic benefit cost Discount rate (a) 5.5 % 3.0 % / 3.1 % 2.8 % / 2.9 % 5.5 % 3.0 % 2.8 % Expected long-term rate of return on plan assets 6.75 % 6.75 % 6.75 % — — — Rate of compensation increase Service-based table Service-based table Service-based table — — — (a) The 2023 discount rate for benefit cost is 5.5% for both the Kirby Pension Plan and the Higman Pension Plan. The 2022 discount rate for benefit cost is 3.0 % for the Kirby Pension Plan and 3.1 % for the Higman Pension Plan. 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 were as follows (in thousands): Other Postretirement Benefits Postretirement Welfare Plan 2023 2022 2021 Components of net periodic benefit cost Interest cost $ 22 $ 17 $ 17 Amortization of actuarial gain ( 344 ) ( 394 ) ( 451 ) Net periodic benefit cost ( 322 ) ( 377 ) ( 434 ) Other changes in benefit obligations recognized in other comprehensive income Current year actuarial loss (gain) 65 ( 58 ) 104 Recognition of actuarial gain 344 394 451 Total recognized in other comprehensive income 409 336 555 Total recognized in net periodic benefit cost and other $ 87 $ ( 41 ) $ 121 Weighted average assumptions used to determine net periodic benefit cost Discount rate 5.5 % 3.0 % 2.8 % Health care cost trend rate: Initial rate 6.50 % 6.25 % 6.50 % Ultimate rate 5.0 % 5.0 % 5.0 % Years to ultimate 2029 2027 2025 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, 2025. 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 2023 and 2022, the Company made contribu tions of $ 0.4 million and $ 0.5 million, respectively, to the SPT. The Company’s contributions to the SPT did not exceed 5 % of total contributions to the SPT in 2022. Total contributions for 2023 are not yet available. The Company did not pay any material surcharges in 2023 and 2022. The federal identification number of the SPT is 13-6100329 and the Certified Zone Status is Green at December 31, 2022. The Company’s future minimum contribution requirements under the SPT are unavailable because actuarial reports for the 2023 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 2022 plan year, the latest period for which a report is availabl e, as the funded status was in excess of 100 %. Based on the most recent communication from the SPT, 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 KDS in New Jersey and expires on October 8, 2028. The Company began participation in the Central Pension Fund of the International Union of Operating Engineers and Participating Employers (“CPF”) with the Stewart & Stevenson LLC 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 2023 and 2022, the Company made contributions of $ 0.6 and $ 0.7 million, respectively, to the CPF. Total contributions for the 2023 plan year are not yet available. The Company did not pay any material surcharges in 2023 and 2022. The federal identification number of the CPF is 36-6052390 and the Certified Zone Status is Green at January 31, 2024. The Company’s future minimum contribution requirements under the CPF are unavailable because actuarial reports for the 2023 plan year, which ended January 31, 2024, 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 2022 plan year, ending January 31, 2023 , the latest period for which a report is available, as the funded status was 107 %. 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 wer e $ 26.9 million, $ 27.9 million, and $ 25.9 million in 2023, 2022, and 2021 , respectively.

Other Comprehensive Income (Los

Other Comprehensive Income (Loss)	12 Months Ended
Other Comprehensive Income (Loss)	Dec. 31, 2023
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax [Abstract]
Other Comprehensive Income (Loss)	(13) Other Comprehensi ve Income (Loss) The Company’s changes in other comprehensive income (loss) were as follows (in thousands): Year Ended December 31, 2023 2022 2021 Gross Income Tax (Provision) Benefit Net Gross Income Tax (Provision) Benefit Net Gross Income Tax Provision Net Pension and postretirement benefits (a): Amortization of net actuarial (gain) loss $ ( 321 ) $ 78 $ ( 243 ) $ ( 330 ) $ 81 $ ( 249 ) $ 3,782 $ ( 952 ) $ 2,830 Actuarial gain 22,438 ( 5,467 ) 16,971 58,147 ( 14,030 ) 44,117 44,491 ( 10,774 ) 33,717 Foreign currency translation adjustments 1,425 — 1,425 ( 1,049 ) — ( 1,049 ) ( 1,061 ) — ( 1,061 ) Total $ 23,542 $ ( 5,389 ) $ 18,153 $ 56,768 $ ( 13,949 ) $ 42,819 $ 47,212 $ ( 11,726 ) $ 35,486 (a) Actuarial gains (losses) are amortized into other income (expense). (See Note 12 – Retirement Plans)

Contingencies and Commitments

Contingencies and Commitments	12 Months Ended
Contingencies and Commitments	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Contingencies and Commitments	(14) Contingencies and Commitments In 2009, the Company was named by the Environmental Protection Agency (the “EPA”) as 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 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. On February 20, 2015, the Company was served as a defendant in a Complaint originally filed on August 14, 2014, in the U.S. District Court of the Southern District of Texas - Houston Division, 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 joined as a member of the PRP Group companies at its pro-rata allocated share. On October 13, 2016, the Company, as a successor to Hollywood Marine, Inc. (“Hollywood Marine”), was issued a General Notice under CERCLA by the EPA in which it was named as a PRP for liabilities associated with the SBA Shipyard Site located near Jennings, Louisiana (the “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, joined the PRP Group Companies. The PRP Group Companies have submitted a draft Study work plan to EPA for their review and comment. 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 accrued a liability, 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 PRPs 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 ATB owned and operated by Kirby Offshore Marine, LLC, a wholly owned subsidiary of the Company, 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 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. On October 10, 2018, the Heiltsuk First Nation filed a civil action in the British Columbia Supreme Court against a subsidiary of the Company, the master and pilot of the tug, the vessels and the Canadian government seeking unquantified damages as a result of the incident. On May 1, 2019, the Company filed a limitation action in the Federal Court of Canada seeking limitation of liability relating to the incident as provided under admiralty law. The Heiltsuk First Nation’s civil claim has been consolidated into the Federal Court limitation action as of July 26, 2019 and it is expected that the Federal Court of Canada will decide all claims against the Company. The Company is unable to estimate the potential exposure in the civil proceeding. 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 its accrual of such estimated liability is adequate 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 its accrual of such estimated liability is adequate 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 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 $ 26.7 million at December 31, 2023, including $ 12.1 million in letters of credit and $ 14.6 million in performance bonds. All of these instruments have an expiration date within two 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.

Related Party Transactions

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions Disclosure [Text Block]	(15) Related Party Transactions David W. Grzebinski, President and Chief Executive Officer of the Company, is a member of the board of directors for ABS, a not- for-profit that provides global classification services to the marine, offshore and gas industries. The Company paid ABS $ 1.5 million in 2023 , $ 1.3 million in 2022 , and $ 1.6 million in 2021 to perform audits and surveys of the Company’s vessels in the ordinary course of business. Mr. Grzebinski is a member of the board of directors of UK Protection & Indemnity Association (“UK P&I”), a mutual marine protection and indemnity organization that provides protection and indemnity insurance for third party liabilities and expenses arising from vessel operations. The Company’s marine fleet is insured on a pro rata share basis through UK P&I and Standard Mutual. The Company p aid $ 3.6 million during 2023 in premiums for coverage in the 2023-2024 pol icy period, $ 3.4 million during 2022 in premiums for coverage in the 2022-2023 policy period, and $ 3.2 million in 2021 in premiums for coverage in the 2021-2022 policy period in the ordinary course of business. Amy D. Husted, Vice President, General Counsel and Secretary of the Company, is a member of the board of directors of Signal Mutual Indemnity Association Ltd (“Signal”), a group self-insurance not-for-profit organization authorized by the U.S. Department of Labor as a longshore worker’s compensation insurance provider. The Company has been a member of Signal since it was established in 1986. The Company paid Signal $ 0.7 million in 2023 , $ 0.5 million in 2022 and $ 0.6 million in 2021 in the ordinary course of business. The husband of Ms. Husted is a partner in the law firm of Clark Hill PLC. The Company paid the law firm $ 0.9 million in 2023 , $ 1.0 million in 2022 , and $ 2.9 million in 2021 for legal services in connection with matters in the ordinary course of business. The brother of Christian G. O’Neil, President of Kirby Inland Marine, LP, Kirby Offshore Marine, LLC, San Jac Marine, LLC and Kirby Offshore Wind, LLC, is a partner in the law firm of W. Sean O’Neil Attorney at Law. The Company paid the law firm $ 0.1 million in 2023 , $ 0.1 million in 2022 , and $ 0.1 million in 2021 for legal services in the ordinary course of business. Rocky B. Dewbre, a director of the Company, serves as President and Chief Operating Officer of Mansfield Service Partners. Mansfield Service Partners is under the same common control as O’Rourke Marine Services (“O’Rourke”), a distributor of lubricants, fuels, and environmental services. The Company paid O’Rourke $ 29.4 million in 2023 in the ordinary course of business .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2023
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. Such reclassifications have no impact on previously reported net earnings (loss), stockholders’ equity, or cash flows.
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-trade as of December 31, 2023 and 2022 wer e $ 136.3 million and $ 139.5 million, respectively, of accruals for revenues earned which have not been invoiced as of the end of each year. Included in accounts receivable-other as of December 31, 2023 and 2022 were $ 29.6 million and $ 27.7 million, respectively, of receivables from insurance companies to cover claims in excess of the Company’s deductible.
Accrued Insurance	Accrued Insurance. The Company’s marine transportation and distribution and services operations are subject to hazards associated with such businesses. The marine transportation business in particular is subject to property damage and casualty risks associated with operating vessels carrying large volumes of bulk liquid and dry cargo in a marine environment. The Company maintains insurance coverage against these hazards with insurance companies subject to a deductible, below which the Company is liable. The Company uses historic experience and actuarial analysis by outside consultants to estimate an appropriate level of accrued insurance liabilities including estimates on individual claims outstanding and an estimated amount for losses that may have occurred but have not been reported to the Company (“IBNR”) or not yet fully developed. If the actual number of claims and magnitude were substantially greater than assumed, the required level of accrued liabilities for claims incurred but not reported or fully developed could be materially understated. Insurance premiums, IBNR losses and incurred claim losses, up to the Company’s deductible for the years ended December 31, 2023, 2022, and 2021, were $ 52.5 million , $ 39.1 million , and $ 37.8 million , respectively.
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, 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. Historically, credit risk with respect to these trade receivables has generally been considered minimal because of the financial strength of the Company’s customers; however, a United States or global recession or other adverse economic condition could impact the collectability of certain customers’ trade receivables which could have a material effect on the Company’s results of operations.
Inventories	Inventories. Inventories are stated at the lower of average cost or net realizable value.
Property, Maintenance and Repairs	Property, Maintenance and Repairs. Property is recorded at cost or acquisition date fair value; improvements and betterments are capitalized as incurred. Depreciation is recorded using 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, improves the operating capacity, or replaces significant components of the vessel, which results in the costs being capitalized. The following table summarizes the balances of property and equipment – net (in thousands): December 31, 2023 2022 Land $ 39,567 $ 38,551 Marine transportation equipment 5,029,653 4,837,379 Buildings and other equipment 641,871 505,942 Construction in progress 112,947 70,271 $ 5,824,038 $ 5,452,143 Accumulated depreciation ( 1,962,933 ) ( 1,818,681 ) Property and equipment – net $ 3,861,105 $ 3,633,462
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, improve the operating capability, or replace significant components of the vessel are capitalized. The Company recognized amortization of major maintenance costs of $ 29.0 million , $ 29.0 million , and $ 33.2 million for the years ended December 31, 2023, 2022, and 2021, 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. For the years ended December 31, 2023, 2022 and 2021 , no interest was capitalized.
Environmental Liabilities	Environmental Liabilities. The Company expenses costs related to environmental events as they are incurred or when a loss is considered probable and reasonably 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 tests at November 30, 2023, 2022, and 2021 . The Company also conducted an interim goodwill impairment test at September 30, 2021. Refer to Note 7, Impairments and other charges for more information. 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 a combination of projected discounted future operating cash flows using an appropriate discount rate and a market approach for comparable companies. The following table summarizes the changes in goodwill (in thousands): Marine Distribution and Total Balance at December 31, 2022 (gross) 505,784 560,155 1,065,939 Accumulated impairment and amortization ( 237,626 ) ( 389,565 ) ( 627,191 ) Balance at December 31, 2022 and 2023 $ 268,158 $ 170,590 $ 438,748
Other Intangibles	Other Intangibles. Other intangibles include assets for favorable contracts and customer relationships, distributorship and dealership agreements, trade names and non-compete agreements and liabilities for unfavorable leases and contracts. The following table summarizes the balances of other intangible assets and other intangible liabilities (in thousands): December 31, 2023 2022 Other intangible assets – gross $ 184,622 $ 203,242 Accumulated amortization ( 141,695 ) ( 151,779 ) Other intangible assets – net $ 42,927 $ 51,463 Other intangible liabilities – gross $ 8,800 $ 13,860 Accumulated amortization ( 8,800 ) ( 13,280 ) Other intangible liabilities – net $ — $ 580 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, 2023, 2022, and 2021, the amortization expense for intangibles was $ 8.1 million , $ 7.6 million , and $ 7.8 million , respectively. Estimated net amortization expense for amortizable intangible assets and liabilities for the next five years (2024 – 2028) is approximat ely $ 8.5 million, $ 8.5 million, $ 6.3 million, $ 5.0 million, and $ 3.5 million, respectively, and $ 11.1 million thereafter. As of December 31, 2023 , the weighted average amortization period for intangible assets and liabilities was approximately seven years .
Revenue Recognition	Revenue Recognition. The majority of marine transportation revenue is derived from term contracts, ranging from one to three years, some of which have renewal options, and the remainder is from spot contracts. The majority of the term contracts by revenue are for terms of one year. The Company provides marine transportation services for its customers and, in almost all cases, does not assume ownership of the products it transports. The Company enters into agreements with its customers to transport cargo from a designated origin to a designated destination at a set rate (affreightment) or at a daily rate (time charter). 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. Time charter or contracts of affreightment of one year or greater are considered term contract revenues and agreements of less than a year are included in spot contract revenues. Spot contracts typically involve an agreement with a customer to move cargo from a specific origin to a designated destination for a rate generally negotiated at the time the cargo movement takes place. Spot contract rates are typically 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. The performance of the service is invoiced as the transaction occurs and payment is required depending on each specific customer’s credit. Distribution products and services are generally sold based upon purchase orders or preferential service agreements with the customer that include fixed or determinable prices. Parts sales are recognized when control transfers to the customer, generally when title passes upon shipment to customers. Service revenue is recognized over time as the service is provided using measures of progress utilizing hours worked or costs incurred as a percentage of estimated hours or expected costs. Revenue from rental agreements is generally recognized on a straight-line basis over the rental period. The Company recognizes the revenues on manufacturing activities upon shipment and transfer of control to the customer. The transactions in the distribution and services segment (“KDS”) are typically invoiced as parts are shipped or upon the completion of the service job. Contract manufacturing activities are generally invoiced upon shipment and the Company will often get deposits from its customers prior to starting work, or progress payments during the project depending on the credit worthiness of the customer and the size of the project.
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 measured at fair value on the date of the grant and the cost for all grants made under the director plan and for grants made under the employee plan is generally recognized ratably over the vesting period of the restricted stock unit (“RSU”), stock option, or restricted stock. The employee plan, however, includes a provision for the continued vesting of unvested stock options and RSUs for employees who meet certain years of service and age requirements at the time of their retirement. The provision results in shorter expense accrual periods on stock options and RSUs granted to employees who are nearing retirement and meet the service and age requirements. Stock option grants are valued at the date of grant as calculated under the Black-Scholes option pricing model. The Company accounts for forfeitures as they occur. The Company’s stock-based compensation plans are more fully described in Note 8, 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.
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 performs an impairment assessment whenever events or changes in circumstances indicate that the carrying amount of long-lived 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 generally 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. If a triggering event is identified, the Company compares the carrying amount of the asset group to the estimated undiscounted future cash flows expected to result from the use of the asset group. If the carrying amount of the asset group exceeds the estimated undiscounted future cash flows, the Company measures the amount of the impairment by comparing the carrying amount of the asset group to its estimated fair value. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell.
Fair Value Measurements	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. The fair value of the Company’s debt instruments is described in Note 5, Long-Term Debt.
Accounting Standards Adoptions	Accounting Standards In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures” (“ASU 2023-09”) which requires entities to disclose additional information in specified categories with respect to the reconciliation of the effective tax rate to the statutory rate for federal, state, and foreign income taxes. ASU 2023-09 is effective for annual and interim periods beginning after December 15, 2023, with early adoption permitted. The Company is currently evaluating the impact that the adoption of this standard will have on its consolidated financial statements. In November 2023, the FASB issued ASU No. 2023-07, “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures” (“ASU 2023-07”) to improve reportable segment disclosure requirements. The amendments require disclosure of significant segment expenses regularly provided to the chief operating decision maker (“CODM”) as well as other segment items, extend certain annual disclosures to interim periods, clarify the applicability to single reportable segment entities, permit more than one measure of profit or loss to be reported under certain conditions, and require disclosure of the title and position of the CODM. ASU 2023-07 is effective for annual periods beginning after December 15, 2024 and for interim periods beginning after December 15, 2025, with early adoption permitted. The Company is currently evaluating the impact that the adoption of this standard will have on its consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
Summary of Significant Accounting Policies (Tables)	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Balances of Property and Equipment - Net	The following table summarizes the balances of property and equipment – net (in thousands): December 31, 2023 2022 Land $ 39,567 $ 38,551 Marine transportation equipment 5,029,653 4,837,379 Buildings and other equipment 641,871 505,942 Construction in progress 112,947 70,271 $ 5,824,038 $ 5,452,143 Accumulated depreciation ( 1,962,933 ) ( 1,818,681 ) Property and equipment – net $ 3,861,105 $ 3,633,462
Changes in Goodwill	The following table summarizes the changes in goodwill (in thousands): Marine Distribution and Total Balance at December 31, 2022 (gross) 505,784 560,155 1,065,939 Accumulated impairment and amortization ( 237,626 ) ( 389,565 ) ( 627,191 ) Balance at December 31, 2022 and 2023 $ 268,158 $ 170,590 $ 438,748
Other Intangible Assets and Other Intangible Liabilities	The following table summarizes the balances of other intangible assets and other intangible liabilities (in thousands): December 31, 2023 2022 Other intangible assets – gross $ 184,622 $ 203,242 Accumulated amortization ( 141,695 ) ( 151,779 ) Other intangible assets – net $ 42,927 $ 51,463 Other intangible liabilities – gross $ 8,800 $ 13,860 Accumulated amortization ( 8,800 ) ( 13,280 ) Other intangible liabilities – net $ — $ 580

Revenues (Tables)

Revenues (Tables)	12 Months Ended
Revenues (Tables)	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue [Table Text Block]	The following table sets forth the Company’s revenues by major source (in thousands): Year Ended December 31, 2023 2022 2021 Marine transportation segment: Inland transportation $ 1,416,483 $ 1,277,010 $ 1,005,145 Coastal transportation 305,454 339,957 317,773 $ 1,721,937 $ 1,616,967 $ 1,322,918 Distribution and services segment: Commercial and industrial $ 802,474 $ 651,566 $ 578,011 Oil and gas 567,229 516,221 345,731 $ 1,369,703 $ 1,167,787 $ 923,742

Segment Data (Tables)

Segment Data (Tables)	12 Months Ended
Segment Data (Tables)	Dec. 31, 2023
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment [Table Text Block]	The following tables set 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 (in thousands): Year Ended December 31, 2023 2022 2021 Revenues: Marine transportation $ 1,721,937 $ 1,616,967 $ 1,322,918 Distribution and services 1,369,703 1,167,787 923,742 $ 3,091,640 $ 2,784,754 $ 2,246,660 Segment profit (loss): Marine transportation $ 238,943 $ 136,184 $ 63,015 Distribution and services 114,481 67,037 27,607 Other ( 59,299 ) ( 38,246 ) ( 381,223 ) $ 294,125 $ 164,975 $ ( 290,601 ) Depreciation and amortization: Marine transportation $ 184,225 $ 177,551 $ 185,979 Distribution and services 19,842 16,776 20,573 Other 7,089 7,116 7,166 $ 211,156 $ 201,443 $ 213,718 Capital expenditures: Marine transportation $ 255,411 $ 147,170 $ 84,353 Distribution and services 140,769 21,713 8,104 Other 5,550 3,723 5,558 $ 401,730 $ 172,606 $ 98,015 December 31, 2023 2022 Total assets: Marine transportation $ 4,454,931 $ 4,285,647 Distribution and services 1,156,384 1,041,841 Other 110,882 227,436 $ 5,722,197 $ 5,554,924
Other Segment Reporting Information	The following table presents the details of “Other” segment profit (loss) (in thousands): Year Ended December 31, 2023 2022 2021 General corporate expenses $ ( 23,341 ) $ ( 18,614 ) $ ( 13,803 ) Gain on disposition of assets 5,009 8,279 5,761 Impairments and other charges — — ( 340,713 ) Interest expense ( 52,008 ) ( 44,588 ) ( 42,469 ) Other income 11,041 16,677 10,001 $ ( 59,299 ) $ ( 38,246 ) $ ( 381,223 ) The following table presents the details of “Other” total assets (in thousands): December 31, 2023 2022 General corporate assets $ 108,306 $ 225,265 Investment in affiliates 2,576 2,171 $ 110,882 $ 227,436

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
Long-Term Debt (Tables)	Dec. 31, 2023
Debt Disclosure [Abstract]
Carrying Values and Fair Values of Debt Outstanding	The following table presents the carrying value and fair value (determined using inputs characteristic of a Level 2 fair value measurement) of debt outstanding (in thousands): December 31, 2023 2022 Carrying Value Fair Value Carrying Value Fair Value Revolving Credit Facility due July 29, 2027 (a) $ 44,000 $ 44,000 $ — $ — Term Loan due July 29, 2027 (a) 170,000 170,000 170,000 170,000 3.29 % senior notes due February 27, 2023 — — 350,000 352,275 4.2 % senior notes due March 1, 2028 500,000 475,920 500,000 477,660 3.46 % senior notes due January 19, 2033 60,000 49,955 60,000 42,647 3.51 % senior notes due January 19, 2033 240,000 200,698 — — Credit Line due June 30, 2024 — — — — Bank notes payable 8,068 8,068 3,292 3,292 1,022,068 948,641 1,083,292 1,045,874 Unamortized debt discounts and issuance costs (b) ( 5,473 ) — ( 3,674 ) — $ 1,016,595 $ 948,641 $ 1,079,618 $ 1,045,874 (a) Variable interest rate of 6.8 % and 5.8 % at December 31, 2023 and 2022, respectively. (b) Excludes $ 1.8 million attributable to the 2027 Revolving Credit Facility included in other assets at December 31, 2022 .
Aggregate Payments due on Long-Term Debt	The aggregate payments due on the long-term debt in each of the next five years were as follows (in thousands): 2024 $ 8,068 2025 32,500 2026 56,250 2027 125,250 2028 500,000 Thereafter 300,000 $ 1,022,068

Leases (Tables)

Leases (Tables)	12 Months Ended
Leases (Tables)	Dec. 31, 2023
Leases [Abstract]
Future Minimum Lease Payments under Operating Leases	Future minimum lease payments under operating leases that have initial noncancelable lease terms in excess of one year were as follows (in thousands): 2024 $ 38,943 2025 27,638 2026 24,945 2027 22,842 2028 18,318 Thereafter 79,755 Total lease payments 212,441 Less: imputed interest ( 40,290 ) Operating lease liabilities $ 172,151
Lease, Cost [Table Text Block]	The following table summarizes lease costs (in thousands): Year Ended December 31, 2023 2022 2021 Operating lease cost $ 42,821 $ 42,319 $ 40,786 Variable lease cost 2,376 1,780 1,793 Short-term lease cost 30,005 25,365 17,914 Sublease income ( 3,223 ) ( 305 ) ( 1,032 ) Total lease cost $ 71,979 $ 69,159 $ 59,461
Operating Leases, Weighted Average Discount Rate and Remaining Lease Term	The following table summarizes other supplemental information about the Company’s operating leases: December 31, 2023 2022 2021 Weighted average discount rate 4.4 % 4.1 % 3.8 % Weighted average remaining lease term 9 years 9 years 9 years

Stock Award Plans (Tables)

Stock Award Plans (Tables)	12 Months Ended
Stock Award Plans (Tables)	Dec. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation Cost Breakdown in Statement of Earnings	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 were as follows (in thousands): Year Ended December 31, 2023 2022 2021 Compensation cost $ 14,941 $ 13,865 $ 15,713 Income tax benefit $ 3,616 $ 3,533 $ 4,410
Stock Option Valuation Assumptions	The key input variables used in valuing the stock options granted were as follows: Year Ended December 31, 2023 Dividend yield None Average risk-free interest rate 3.7 % Stock price volatility 35 % Estimated option term 7 years
Employee Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock Option Activity	The following is a summary of the stock option activity under the employee plan described above: Outstanding Weighted Outstanding at December 31, 2022 396,165 $ 70.06 Exercised ( 117,896 ) $ 60.84 Expired ( 23,024 ) $ 73.66 Outstanding at December 31, 2023 255,245 $ 74.00
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, 2023: Options Outstanding Options Exercisable Range of Exercise Number Weighted Weighted Aggregated Number Weighted Aggregated $ 64.89 15,500 1.3 $ 64.89 15,500 $ 64.89 $ 73.29 – $ 75.50 233,040 2.1 $ 74.29 233,040 $ 74.29 $ 84.90 6,705 2.3 $ 84.90 6,705 $ 84.90 $ 64.89 – $ 84.90 255,245 2.0 $ 74.00 $ 1,187 255,245 $ 74.00 $ 1,187
RSU Activity	The following is a summary of RSU activity under the employee plan described above: Unvested RSUs Weighted Nonvested balance at December 31, 2022 558,819 $ 62.13 Granted 184,440 $ 72.23 Vested ( 161,550 ) $ 64.85 Forfeited ( 27,105 ) $ 63.68 Nonvested balance at December 31, 2023 554,604 $ 64.61
Director Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock Option Activity	The following is a summary of the stock option activity under the director plan described above: Outstanding Weighted Outstanding at December 31, 2022 56,480 $ 86.19 Granted 3,865 $ 72.83 Exercised — $ — Expired ( 30,000 ) $ 80.04 Outstanding at December 31, 2023 30,345 $ 90.57
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, 2023: Options Outstanding Options Exercisable Range of Exercise Number Weighted Weighted Aggregate Number Weighted Aggregate $ 70.65 – $ 73.57 7,053 6.6 $ 71.85 6,278 $ 71.75 $ 84.90 – $ 85.30 5,292 4.8 $ 85.10 5,292 $ 85.10 $ 99.52 18,000 0.3 $ 99.52 18,000 $ 99.52 $ 70.65 – $ 99.52 30,345 2.6 $ 90.57 $ 47 29,570 $ 91.04 $ 42
Restricted Stock Award Activity	The following is a summary of the restricted stock award activity under the director plan described above: Unvested Weighted Nonvested balance at December 31, 2022 1,698 $ 65.36 Granted 31,526 $ 72.67 Vested ( 32,604 ) $ 72.29 Nonvested balance at December 31, 2023 620 $ 72.65

Taxes on Income (Tables)

Taxes on Income (Tables)	12 Months Ended
Taxes on Income (Tables)	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Earnings (Loss) Before Taxes	Earnings (loss) before taxes on income and details of the provision (benefit) for taxes on income were as follows (in thousands): Year Ended December 31, 2023 2022 2021 Earnings (loss) before taxes on income: United States $ 293,011 $ 164,590 $ ( 290,181 ) Foreign 1,114 385 ( 420 ) $ 294,125 $ 164,975 $ ( 290,601 ) Provision (benefit) for taxes on income: U.S. Federal: Current $ ( 41 ) $ 513 $ ( 460 ) Deferred 61,205 34,980 ( 48,843 ) $ 61,164 $ 35,493 $ ( 49,303 ) U.S. State: Current $ 5,498 $ 3,793 $ 1,560 Deferred 4,093 2,802 4,424 $ 9,591 $ 6,595 $ 5,984 Foreign: Current $ 465 $ 126 $ ( 511 ) $ 465 $ 126 $ ( 511 ) Consolidated: Current $ 5,922 $ 4,432 $ 589 Deferred 65,298 37,782 ( 44,419 ) $ 71,220 $ 42,214 $ ( 43,830 )
Effective Income Tax Rate Reconciliation	The Company’s provision (benefit) for taxes on income varied from the statutory federal income tax rate due to the following: Year Ended December 31, 2023 2022 2021 United States income tax statutory rate 21.0 % 21.0 % 21.0 % State and local taxes, net of federal benefit 2.6 3.1 ( 1.7 ) Other – net 0.6 1.5 ( 4.2 ) 24.2 % 25.6 % 15.1 %
Deferred Tax Assets and Liabilities	The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and liabilities were as follows (in thousands): December 31, 2023 2022 Deferred tax assets: Allowance for doubtful accounts $ 1,549 $ 1,556 Inventory 10,500 11,679 Insurance accruals 6,077 4,856 Deferred compensation 11,441 7,703 Unrealized gain on defined benefit plans ( 9,982 ) ( 5,532 ) Goodwill and other intangibles 39,719 52,847 Operating loss carryforwards 52,082 79,699 Retirement benefits 3,548 5,472 Other 13,467 9,962 128,401 168,242 Valuation allowances ( 22,073 ) ( 19,960 ) 106,328 148,282 Deferred tax liabilities: Property ( 695,233 ) ( 671,830 ) Deferred state taxes ( 90,457 ) ( 87,445 ) Other ( 17,195 ) ( 14,891 ) ( 802,885 ) ( 774,166 ) $ ( 696,557 ) $ ( 625,884 )
Reconciliation of Liability for Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of the liability for unrecognized tax benefits is as follows (in thousands): Year Ended December 31, 2023 2022 2021 Balance at beginning of year $ 662 $ 737 $ 783 Additions based on tax positions related to the current year — 13 13 Additions for tax positions of prior years — 66 281 Reductions for tax positions of prior years ( 14 ) ( 154 ) ( 340 ) Balance at end of year $ 648 $ 662 $ 737

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
Earnings Per Share (Tables)	Dec. 31, 2023
Earnings Per Share [Abstract]
Schedule of Loss Per Share	The following table presents the components of basic and diluted earnings (loss) per share (in thousands, except per share amounts): Year Ended December 31, 2023 2022 2021 Net earnings (loss) attributable to Kirby $ 222,935 $ 122,291 $ ( 246,954 ) Undistributed earnings allocated to restricted shares ( 62 ) ( 33 ) — Earnings (loss) available to Kirby common stockholders — basic 222,873 122,258 ( 246,954 ) Undistributed earnings allocated to restricted shares 62 33 — Undistributed earnings reallocated to restricted shares ( 62 ) ( 33 ) — Earnings (loss) available to Kirby common stockholders — diluted $ 222,873 $ 122,258 $ ( 246,954 ) Shares outstanding: Weighted average common stock issued and outstanding 59,548 60,055 60,099 Weighted average unvested restricted stock ( 17 ) ( 17 ) ( 46 ) Weighted average common stock outstanding — basic 59,531 60,038 60,053 Dilutive effect of stock options and restricted stock units 326 291 — Weighted average common stock outstanding — diluted 59,857 60,329 60,053 Net earnings (loss) per share attributable to Kirby common stockholders: Basic $ 3.74 $ 2.04 $ ( 4.11 ) Diluted $ 3.72 $ 2.03 $ ( 4.11 )

Inventories (Tables)

Inventories (Tables)	12 Months Ended
Inventories (Tables)	Dec. 31, 2023
Inventory Disclosure [Abstract]
Schedule of Inventories, Net	The following table presents the details of inventories — net (in thousands): December 31, 2023 2022 Finished goods $ 351,050 $ 358,702 Work in process 103,339 103,146 $ 454,389 $ 461,848

Retirement Plans (Tables)

Retirement Plans (Tables)	12 Months Ended
Retirement Plans (Tables)	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Asset Allocation	The aggregate fair value of plan assets of the Company’s pension plans was $ 375.9 million and $ 341.1 million at December 31, 2023 and 2022, respectively. Pension assets were allocated among asset categories as follows: December 31, Current Asset Category 2023 2022 Allocation Policy U.S. equity securities 51 % 50 % 45 % — 50 % — 55 % International equity securities 20 20 12 % — 20 % — 28 % Debt securities 29 30 20 % — 30 % — 40 % Cash and cash equivalents — — 0 % — 0 % — 0 % 100 % 100 %
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): Pension Benefits Other Postretirement Benefits Pension Plans SERP Postretirement Welfare Plan 2023 2022 2023 2022 2023 2022 Change in benefit obligation Benefit obligation at beginning of year $ 339,509 $ 495,272 $ 833 $ 1,033 $ 432 $ 582 Service cost 3,695 6,538 — — — — Interest cost 18,356 14,779 43 29 22 17 Actuarial (gain) loss 13,241 ( 158,816 ) 91 ( 74 ) 65 ( 58 ) Gross benefits paid ( 32,052 ) ( 12,665 ) ( 153 ) ( 155 ) ( 104 ) ( 109 ) Settlements — ( 5,599 ) — — — — Benefit obligation at end of year $ 342,749 $ 339,509 $ 814 $ 833 $ 415 $ 432 Accumulated benefit obligation at end of year $ 326,987 $ 325,274 $ 814 $ 833 $ 415 $ 432 Weighted-average assumption used to determine benefit obligation at end of year Discount rate (a) 5.1 %/ 5.2 % 5.5 % 5.1 % 5.5 % 5.1 % 5.5 % Rate of compensation increase Service-based table Service-based table — — — — Health care cost trend rate Initial rate — — — — 6.25 % 6.50 % Ultimate rate — — — — 5.0 % 5.0 % Years to ultimate — — — — 2029 2029 Change in plan assets Fair value of plan assets at beginning of year $ 341,061 $ 430,821 $ — $ — $ — $ — Actual return on plan assets 58,734 ( 72,402 ) — — — — Employer contribution 8,174 906 153 155 104 109 Gross benefits paid ( 32,052 ) ( 12,665 ) ( 153 ) ( 155 ) ( 104 ) ( 109 ) Settlements — ( 5,599 ) — — — — Fair value of plan assets at end of year $ 375,917 $ 341,061 $ — $ — $ — $ — (a) The 2023 discount rate was 5.1 % for the Kirby Pension Plan and 5.2 % for the Higman Pension Plan. The 2022 discount rate was 5.5 % for both the Kirby Pension Plan and the Higman Pension Plan.
Funded Status at End of Year	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 (in thousands): Pension Benefits Other Postretirement Benefits Pension Plans SERP Postretirement Welfare Plan 2023 2022 2023 2022 2023 2022 Funded status at end of year Fair value of plan assets $ 375,917 $ 341,061 $ — $ — $ — $ — Benefit obligations ( 342,749 ) ( 339,509 ) ( 814 ) ( 833 ) ( 415 ) ( 432 ) Funded status and amount recognized at end of year $ 33,168 $ 1,552 $ ( 814 ) $ ( 833 ) $ ( 415 ) $ ( 432 ) Amounts recognized in the consolidated balance sheets Noncurrent asset 42,698 18,695 — — — — Current liability — — ( 106 ) ( 106 ) ( 46 ) ( 49 ) Long-term liability ( 9,530 ) ( 17,143 ) ( 708 ) ( 727 ) ( 369 ) ( 383 ) Amounts recognized in accumulated other comprehensive income Net actuarial (gain) loss $ ( 48,033 ) $ ( 25,449 ) $ 391 $ 324 $ ( 1,890 ) $ ( 2,299 ) Prior service cost (credit) — — — — — — Accumulated other compensation income $ ( 48,033 ) $ ( 25,449 ) $ 391 $ 324 $ ( 1,890 ) $ ( 2,299 )
Expected Cash Flows for the Defined Benefit Plans and Postretirement Benefit Plan	The following table presents the expected cash flows for the Company’s defined benefit plans and postretirement benefit plan (in thousands): Pension Benefits Other Postretirement Benefits Pension Plans SERP Postretirement Welfare Plan 2023 2022 2023 2022 2023 2022 Expected employer contributions First year $ 1,770 $ 8,374 $ — $ — $ — $ — Expected benefit payments (gross) Year one $ 16,696 $ 16,312 $ 108 $ 108 $ 47 $ 50 Year two 17,513 16,899 103 104 46 49 Year three 18,169 17,808 98 99 44 47 Year four 19,096 18,650 93 94 43 45 Year five 19,860 19,707 88 90 41 43 Next five years 108,717 110,417 337 359 167 176
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit Cost	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 were as follows (in thousands): Pension Benefits Pension Plans SERP 2023 2022 2021 2023 2022 2021 Components of net periodic benefit cost Service cost $ 3,695 $ 6,538 $ 7,961 $ — $ — $ — Interest cost 18,356 14,779 14,239 43 29 31 Expected return on plan assets ( 22,910 ) ( 28,399 ) ( 26,244 ) — — — Amortization of actuarial loss — 34 4,193 23 30 40 Net periodic benefit cost ( 859 ) ( 7,048 ) 149 66 59 71 Other changes in plan assets and benefit obligations recognized in other comprehensive income Current year actuarial (gain) loss ( 22,583 ) ( 58,015 ) ( 44,583 ) 91 ( 74 ) ( 12 ) Recognition of actuarial loss — ( 34 ) ( 4,193 ) ( 23 ) ( 30 ) ( 40 ) Total recognized in other comprehensive income ( 22,583 ) ( 58,049 ) ( 48,776 ) 68 ( 104 ) ( 52 ) Total recognized in net periodic benefit cost and other comprehensive income $ ( 23,442 ) $ ( 65,097 ) $ ( 48,627 ) $ 134 $ ( 45 ) $ 19 Weighted average assumptions used to determine net periodic benefit cost Discount rate (a) 5.5 % 3.0 % / 3.1 % 2.8 % / 2.9 % 5.5 % 3.0 % 2.8 % Expected long-term rate of return on plan assets 6.75 % 6.75 % 6.75 % — — — Rate of compensation increase Service-based table Service-based table Service-based table — — — (a) The 2023 discount rate for benefit cost is 5.5% for both the Kirby Pension Plan and the Higman Pension Plan. The 2022 discount rate for benefit cost is 3.0 % for the Kirby Pension Plan and 3.1 % for the Higman Pension Plan.
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit Cost	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 were as follows (in thousands): Other Postretirement Benefits Postretirement Welfare Plan 2023 2022 2021 Components of net periodic benefit cost Interest cost $ 22 $ 17 $ 17 Amortization of actuarial gain ( 344 ) ( 394 ) ( 451 ) Net periodic benefit cost ( 322 ) ( 377 ) ( 434 ) Other changes in benefit obligations recognized in other comprehensive income Current year actuarial loss (gain) 65 ( 58 ) 104 Recognition of actuarial gain 344 394 451 Total recognized in other comprehensive income 409 336 555 Total recognized in net periodic benefit cost and other $ 87 $ ( 41 ) $ 121 Weighted average assumptions used to determine net periodic benefit cost Discount rate 5.5 % 3.0 % 2.8 % Health care cost trend rate: Initial rate 6.50 % 6.25 % 6.50 % Ultimate rate 5.0 % 5.0 % 5.0 % Years to ultimate 2029 2027 2025

Other Comprehensive Income (L_2

Other Comprehensive Income (Loss) (Tables)	12 Months Ended
Other Comprehensive Income (Loss) (Tables)	Dec. 31, 2023
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax [Abstract]
Changes in Other Comprehensive Income (Loss)	The Company’s changes in other comprehensive income (loss) were as follows (in thousands): Year Ended December 31, 2023 2022 2021 Gross Income Tax (Provision) Benefit Net Gross Income Tax (Provision) Benefit Net Gross Income Tax Provision Net Pension and postretirement benefits (a): Amortization of net actuarial (gain) loss $ ( 321 ) $ 78 $ ( 243 ) $ ( 330 ) $ 81 $ ( 249 ) $ 3,782 $ ( 952 ) $ 2,830 Actuarial gain 22,438 ( 5,467 ) 16,971 58,147 ( 14,030 ) 44,117 44,491 ( 10,774 ) 33,717 Foreign currency translation adjustments 1,425 — 1,425 ( 1,049 ) — ( 1,049 ) ( 1,061 ) — ( 1,061 ) Total $ 23,542 $ ( 5,389 ) $ 18,153 $ 56,768 $ ( 13,949 ) $ 42,819 $ 47,212 $ ( 11,726 ) $ 35,486 (a) Actuarial gains (losses) are amortized into other income (expense). (See Note 12 – Retirement Plans)

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Receivables [Abstract]
Accruals for revenues earned included in accounts receivable	$ 136,300	$ 139,500
Receivables from insurance companies to cover claims in excess included in accounts receivable	$ 29,600	27,700
Drydocking on Ocean-Going Vessels [Abstract]
Period in which recertification of ocean going vessels occur twice	5 years
Recognized amortization of major maintenance costs	$ 29,000	29,000	$ 33,200
Capitalized interest excluded from interest expense	$ 0	$ 0	$ 0
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, Plant and Equipment [Abstract]
Property, Plant and Equipment, Useful Life	5 years
Marine Transportation Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Useful Life	40 years
Buildings [Member] \| Minimum [Member]
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Useful Life	10 years
Buildings [Member] \| Maximum [Member]
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Useful Life	40 years
Other Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Useful Life	2 years
Other Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment, Useful Life	10 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies, Summary of Balances of Property and Equipment - Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 5,824,038	$ 5,452,143
Accumulated depreciation	(1,962,933)	(1,818,681)
Property and equipment - net	3,861,105	3,633,462
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	39,567	38,551
Marine Transportation Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,029,653	4,837,379
Buildings and Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	641,871	505,942
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 112,947	$ 70,271

Summary of Significant Accoun_6

Summary of Significant Accounting Policies, Goodwill and Other Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Balance (gross)	$ 1,065,939
Accumulated impairment and amortization	(627,191)
Balance	438,748
Balance (gross)		$ 1,065,939
Accumulated impairment and amortization	(627,191)	(627,191)
Balance	438,748	438,748
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Other intangible assets - gross	184,622	203,242
Accumulated amortization	(141,695)	(151,779)
Other intangible assets - net	42,927	51,463
Other intangible liabilities - gross	8,800	13,860
Accumulated amortization	(8,800)	(13,280)
Other intangible liabilities - net	0	580
Amortization of Intangible Assets	8,100	7,600	$ 7,800
Intangible Assets and liabilities, Estimated Amortization Expense, Fiscal Year Maturity [Abstract]
2024	8,500
2025	8,500
2026	6,300
2027	5,000
2028	3,500
Thereafter	$ 11,100
Weighted average amortization period for intangible assets and liabilities	7 years
Marine Transportation Segment [Member]
Goodwill and Intangible Assets Disclosure [Abstract]
Balance (gross)	$ 505,784
Accumulated impairment and amortization	(237,626)
Balance	268,158
Balance (gross)		505,784
Accumulated impairment and amortization	(237,626)	(237,626)
Balance	268,158	268,158
Distribution and Services Segment [Member]
Goodwill and Intangible Assets Disclosure [Abstract]
Balance (gross)	560,155
Accumulated impairment and amortization	(389,565)
Balance	170,590
Balance (gross)		560,155
Accumulated impairment and amortization	(389,565)	(389,565)
Balance	$ 170,590	$ 170,590

Summary of Significant Accoun_7

Summary of Significant Accounting Policies, Revenue Recognition through Accrued Insurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Insurance [Abstract]
Accrued insurance liabilities	$ 52.5	$ 39.1	$ 37.8
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	3 years

Acquisitions (Details)

Acquisitions (Details) $ in Thousands				9 Months Ended	12 Months Ended
Acquisitions (Details) $ in Thousands	Jul. 14, 2023 USD ($) Barge Barrels	Mar. 31, 2022 USD ($)	Oct. 04, 2021 USD ($)	Sep. 30, 2023 USD ($) Barge	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($) Vessel
Restructuring Cost and Reserve [Line Items]
Cash paid for acquisition					$ 401,730	$ 172,606	$ 98,015
Inland Tank Barges [Member]
Restructuring Cost and Reserve [Line Items]
Number of tank barges \| Barge	23			4
Total capacity of barrels \| Barrels	265,000
Cash paid for acquisition	$ 37,000
Number of maritime vessels acquired \| Vessel							4
Cash paid for acquisition				$ 500			$ 7,500
Average age	14 years
Energy Storage System [Member]
Restructuring Cost and Reserve [Line Items]
Cash paid for acquisition			$ 1,600
Gearbox Repair [Member]
Restructuring Cost and Reserve [Line Items]
Cash paid for acquisition		$ 3,900

Revenues (Details)

Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
Revenues (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Abstract]
Revenues by major source	$ 3,091,640	$ 2,784,754	$ 2,246,660
Revenue recognized	84,000	61,700	40,900
Marine Transportation [Member]
Disaggregation of Revenue [Abstract]
Revenues by major source	1,721,937	1,616,967	1,322,918
Marine Transportation [Member] \| Inland Transportation [Member]
Disaggregation of Revenue [Abstract]
Revenues by major source	1,416,483	1,277,010	1,005,145
Marine Transportation [Member] \| Coastal Transportation [Member]
Disaggregation of Revenue [Abstract]
Revenues by major source	305,454	339,957	317,773
Distribution and Services [Member]
Disaggregation of Revenue [Abstract]
Revenues by major source	1,369,703	1,167,787	923,742
Distribution and Services [Member] \| Commercial and Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenues by major source	802,474	651,566	578,011
Distribution and Services [Member] \| Oil and Gas [Member]
Disaggregation of Revenue [Abstract]
Revenues by major source	$ 567,229	$ 516,221	$ 345,731

Revenues, Remaining Performance

Revenues, Remaining Performance Obligation (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Contract assets	$ 0	$ 0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year

Segment Data (Details)

Segment Data (Details) $ in Thousands	12 Months Ended
Segment Data (Details) $ in Thousands	Dec. 31, 2023 USD ($) Segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| Segment	2
Revenues [Abstract]
Revenues	$ 3,091,640	$ 2,784,754	$ 2,246,660
Segment profit (loss)	294,125	164,975	(290,601)
Total assets	5,722,197	5,554,924
Depreciation and amortization	211,156	201,443	213,718
Capital expenditures	401,730	172,606	98,015
Other segment disclosures [Abstract]
Gain on disposition of assets	5,009	8,279	5,761
Interest expense	(52,008)	(44,588)	(42,469)
Earnings (loss) before taxes on income	294,125	164,975	(290,601)
Other Assets [Abstract]
Investment in affiliates	2,576	2,171
Marine Transportation [Member]
Revenues [Abstract]
Revenues	1,721,937	1,616,967	1,322,918
Distribution and Services [Member]
Revenues [Abstract]
Revenues	1,369,703	1,167,787	923,742
Other [Member]
Revenues [Abstract]
Segment profit (loss)	(59,299)	(38,246)	(381,223)
Total assets	110,882	227,436
Depreciation and amortization	7,089	7,116	7,166
Capital expenditures	5,550	3,723	5,558
Other segment disclosures [Abstract]
General corporate expenses	(23,341)	(18,614)	(13,803)
Gain on disposition of assets	5,009	8,279	5,761
Impairments and other charges	0	0	(340,713)
Interest expense	(52,008)	(44,588)	(42,469)
Other income	11,041	16,677	10,001
Earnings (loss) before taxes on income	(59,299)	(38,246)	(381,223)
Other Assets [Abstract]
General corporate assets	108,306	225,265
Investment in affiliates	2,576	2,171
Total other assets	110,882	227,436
Reportable Segments [Member] \| Marine Transportation [Member]
Revenues [Abstract]
Revenues	1,721,937	1,616,967	1,322,918
Segment profit (loss)	238,943	136,184	63,015
Total assets	4,454,931	4,285,647
Depreciation and amortization	184,225	177,551	185,979
Capital expenditures	255,411	147,170	84,353
Other segment disclosures [Abstract]
Earnings (loss) before taxes on income	238,943	136,184	63,015
Reportable Segments [Member] \| Distribution and Services [Member]
Revenues [Abstract]
Revenues	1,369,703	1,167,787	923,742
Segment profit (loss)	114,481	67,037	27,607
Total assets	1,156,384	1,041,841
Depreciation and amortization	19,842	16,776	20,573
Capital expenditures	140,769	21,713	8,104
Other segment disclosures [Abstract]
Earnings (loss) before taxes on income	114,481	67,037	27,607
Intersegment Eliminations [Member]
Revenues [Abstract]
Revenues	39,800	31,900	23,600
Segment profit (loss)	4,000	3,200	2,400
Other segment disclosures [Abstract]
Earnings (loss) before taxes on income	$ 4,000	$ 3,200	$ 2,400

Long-Term Debt, Carrying Value

Long-Term Debt, Carrying Value and Fair Value of Debt Outstanding (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 29, 2022	Dec. 31, 2023	Dec. 31, 2022
Carrying Value and Fair Value of Debt Outstanding [Abstract]
Carrying value		$ 1,022,068	$ 1,083,292
Fair value		948,641	1,045,874
Unamortized debt discounts and issuance costs		(5,473)	(3,674)
Long-term debt		1,016,595	1,079,618
Debt Instrument, Basis Spread on Variable Rate	0.50%
Amount excluded on unamortized debt discounts and issuance costs			1,800
3.29% Senior Notes Due February, 27 2023 [Member]
Carrying Value and Fair Value of Debt Outstanding [Abstract]
Carrying value		0	350,000
Fair value		$ 0	352,275
Interest rate		3.29%
Maturity Date		Feb. 27, 2023
4.2% Senior Notes Due March 1, 2028 [Member]
Carrying Value and Fair Value of Debt Outstanding [Abstract]
Carrying value		$ 500,000	500,000
Fair value		$ 475,920	477,660
Interest rate		4.20%
Maturity Date		Mar. 01, 2028
3.46% Senior Notes Due January 19, 2033 [Member]
Carrying Value and Fair Value of Debt Outstanding [Abstract]
Carrying value		$ 60,000	60,000
Fair value		$ 49,955	42,647
Interest rate		3.46%
Maturity Date		Jan. 19, 2033
3.51% senior notes due January 19, 2033 [Member]
Carrying Value and Fair Value of Debt Outstanding [Abstract]
Carrying value		$ 240,000	0
Fair value		$ 200,698	0
Interest rate		3.51%
Maturity Date		Jan. 19, 2033
Credit Line Due June 30, 2024 [Member]
Carrying Value and Fair Value of Debt Outstanding [Abstract]
Carrying value		$ 0	0
Fair value		$ 0	0
Maturity Date		Jun. 30, 2024
Bank Note Payable [Member]
Carrying Value and Fair Value of Debt Outstanding [Abstract]
Carrying value		$ 8,068	3,292
Fair value		8,068	3,292
Revolving Credit Facility [Member]
Carrying Value and Fair Value of Debt Outstanding [Abstract]
Carrying value		44,000	0
Fair value		$ 44,000	0
Maturity Date		Jul. 29, 2027
Term Loan [Member]
Carrying Value and Fair Value of Debt Outstanding [Abstract]
Long-term debt	$ 250,000
Term Loan Due July 29,2027 [Member]
Carrying Value and Fair Value of Debt Outstanding [Abstract]
Carrying value		$ 170,000	170,000
Fair value		$ 170,000	$ 170,000
Debt Instrument, Basis Spread on Variable Rate		6.80%	5.80%
Maturity Date		Jul. 29, 2027

Long-Term Debt, Schedule of Agg

Long-Term Debt, Schedule of Aggregate Payments Due on Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Disclosure [Abstract]
2024	$ 8,068
2025	32,500
2026	56,250
2027	125,250
2028	500,000
Thereafter	300,000
Carrying value	$ 1,022,068	$ 1,083,292

Long-Term Debt (Details)

Long-Term Debt (Details) - USD ($)					1 Months Ended	3 Months Ended	12 Months Ended
Long-Term Debt (Details) - USD ($)	Jun. 30, 2025	Jul. 19, 2023	Jan. 19, 2023	Feb. 03, 2022	Jul. 29, 2022	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Long-term Debt [Abstract]
Payments on long-term debt							$ 350,000,000	$ 395,000,000	$ 60,000,000
Term loan						$ 1,079,618,000	1,016,595,000	1,079,618,000
Unpaid balance					$ 43,800,000
Debt Instrument, Basis Spread on Variable Rate					0.50%
Senior Notes Due March 1, 2028 [Member]
Long-term Debt [Abstract]
Long term debt, face amount							$ 500,000,000
Interest rate							4.20%
Maturity Date							Mar. 01, 2028
Debt Instrument, Periodic Payment, Interest							$ 10,500,000
Senior Notes Series B Due February 27, 2023 [Member]
Long-term Debt [Abstract]
Interest rate							3.29%
Maturity Date							Feb. 27, 2023
3.46 Series A Notes Due January 19, 2023 [Member]
Long-term Debt [Abstract]
Long term debt, face amount				$ 60,000,000
Interest rate				3.46%
Maturity Date				Jan. 19, 2033
3.51 Series B Notes Due January 19, 2023 [Member]
Long-term Debt [Abstract]
Long term debt, face amount				$ 240,000,000
Interest rate				3.51%
Maturity Date				Jan. 19, 2033
Debt Instrument, Periodic Payment, Interest		$ 5,300,000	$ 500,000
SOFR [Member]
Long-term Debt [Abstract]
Interest rate					1%
Revolving Credit Facility [Member]
Long-term Debt [Abstract]
Maturity Date							Jul. 29, 2027
Maximum borrowing capacity					$ 500,000,000		$ 850,000,000
Credit facility, amount outstanding							6,000
Available borrowing capacity					35,000,000		$ 456,000,000
Commitment Amount					$ 25,000
Revolving Credit Facility [Member] \| SOFR [Member]
Long-term Debt [Abstract]
Debt Instrument, Basis Spread on Variable Rate					137.50%
Revolving Credit Facility [Member] \| Base Rate [Member]
Long-term Debt [Abstract]
Debt Instrument, Basis Spread on Variable Rate					37.50%
Term Loan [Member]
Long-term Debt [Abstract]
Payments on long-term debt					$ 250,000,000	80,000,000
Term loan					$ 250,000,000
Credit facility, expiration date					Jul. 29, 2027		Mar. 27, 2024
Term Loan [Member] \| Forecast [Member]
Long-term Debt [Abstract]
Payments on long-term debt	$ 0
Line Of Credit [Member]
Long-term Debt [Abstract]
Maximum borrowing capacity							$ 10,000,000
Credit facility, expiration date							Jun. 30, 2024
Credit facility, amount outstanding							$ 7,300,000
Available borrowing capacity							2,700,000
Secured Debt [Member]
Long-term Debt [Abstract]
Short-Term Debt						$ 3,300,000	$ 8,100,000	$ 3,300,000
Unsecured Debt [Member]
Long-term Debt [Abstract]
Long term debt, face amount				$ 300,000,000

Leases, Future Minimum Lease Pa

Leases, Future Minimum Lease Payments Under Operating Leases (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Leases [Abstract]
Percentage of costs relate to service costs for leased towing vessels	70%
Future Minimum Lease Payments Under Operating Leases [Abstract]
2024	$ 38,943
2025	27,638
2026	24,945
2027	22,842
2028	18,318
Thereafter	79,755
Total lease payments	212,441
Less: imputed interest	(40,290)
Operating lease liabilities	$ 172,151

Leases, Lease Cost (Details)

Leases, Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
Leases, Lease Cost (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lease, Cost [Abstract]
Operating lease cost	$ 42,821	$ 42,319	$ 40,786
Variable lease cost	2,376	1,780	1,793
Short-term lease cost	30,005	25,365	17,914
Sublease income	(3,223)	(305)	(1,032)
Total lease cost	$ 71,979	$ 69,159	$ 59,461

Leases, Other Supplemental Info

Leases, Other Supplemental Information (Details)	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Supplemental Information about Operating Leases [Abstract]
Weighted average discount rate	4.40%	4.10%	3.80%
Weighted average remaining lease term	9 years	9 years	9 years

Impairments and Other Charges (

Impairments and Other Charges (Details) $ in Thousands	3 Months Ended	12 Months Ended
Impairments and Other Charges (Details) $ in Thousands	Sep. 30, 2021 USD ($)	Dec. 31, 2023 USD ($) Segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Impairment Effects on Earnings Per Share [Line Items]
Proceeds from sale of assets		$ 26,081	$ 36,905	$ 51,342
Impairment, Intangible Asset, Finite-Lived, Statement of Income or Comprehensive Income [Extensible Enumeration]	Asset Impairment Charges
Marine Transportation [Member]
Impairment Effects on Earnings Per Share [Line Items]
Number of reporting units \| Segment		1
Goodwill impairment charge	$ 219,100
Level 3 [Member] \| Marine Transportation [Member]
Impairment Effects on Earnings Per Share [Line Items]
Non-cash pre-tax impairment charge	24,200
HAWAII \| Marine Transportation [Member]
Impairment Effects on Earnings Per Share [Line Items]
Proceeds from sale of assets	17,200
Impairment of Intangible Assets, Finite-Lived	$ 97,500

Stock Award Plans, Compensation

Stock Award Plans, Compensation Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Payment Arrangement [Abstract]
Compensation cost	$ 14,941	$ 13,865	$ 15,713
Income tax benefit	$ 3,616	$ 3,533	$ 4,410

Stock Award Plans, Employee Pla

Stock Award Plans, Employee Plan Stock Option Activity (Details) - Employee Stock Award Plan [Member]	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Employee Stock Option [Member]
Stock Award Plan Information [Abstract]
Term of grant	7 years
Vesting period	3 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at Period Start (in shares)	396,165
Exercised (in shares)	(117,896)
Expired (in shares)	(23,024)
Outstanding at Period End (in shares)	255,245
Weighted Average Exercise Price [Abstract]
Outstanding at Period Start (in dollars per share) \| $ / shares	$ 70.06
Exercised (in dollars per share) \| $ / shares	60.84
Expired (in dollars per share) \| $ / shares	73.66
Outstanding at Period End (in dollars per share) \| $ / shares	$ 74
Stock Appreciation Rights (SARs)
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at Period End (in shares)	0
Restricted Stock Units (RSUs) [Member]
Stock Award Plan Information [Abstract]
Vesting period	5 years

Stock Award Plans, Employee P_2

Stock Award Plans, Employee Plan Outstanding and Exercisable Options (Details) - Employee Stock Award Plan [Member] - Employee Stock Option [Member] $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
First Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, upper limit (in dollars per share)	$ 64.89
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	15,500
Weighted Average Remaining Contractual Life	1 year 3 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 64.89
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	15,500
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 64.89
Second Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	73.29
Range of Exercise Prices, upper limit (in dollars per share)	$ 75.5
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	233,040
Weighted Average Remaining Contractual Life	2 years 1 month 6 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 74.29
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	233,040
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 74.29
Third Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	$ 84.9
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	6,705
Weighted Average Remaining Contractual Life	2 years 3 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 84.9
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	6,705
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 84.9
Full Exercise Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	64.89
Range of Exercise Prices, upper limit (in dollars per share)	$ 84.9
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	255,245
Weighted Average Remaining Contractual Life	2 years
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 74
Aggregate Intrinsic Value, Options Outstanding \| $	$ 1,187
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	255,245
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 74
Aggregate Intrinsic Value, Options Exercisable \| $	$ 1,187

Stock Award Plans, Employee P_3

Stock Award Plans, Employee Plan Restricted Stock Award Activity (Details) - Employee Stock Award Plan [Member] - Restricted Stock [Member] - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period	0	0	0
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number	0	0

Stock Award Plans, Employee P_4

Stock Award Plans, Employee Plan RSU Activity (Details) - Employee Stock Award Plan [Member] - Restricted Stock Units (RSUs) [Member] - $ / shares	1 Months Ended	12 Months Ended
	Feb. 29, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested balance beginning of period (in shares)		558,819
Granted (in shares)		184,440
Vested (in shares)		(161,550)
Forfeited (in shares)		(27,105)
Nonvested balance end of period (in shares)		554,604	558,819
Weighted Average Grant Date Fair Value Per Share [Abstract]
Nonvested balance beginning of period (in dollars per share)		$ 62.13
Granted (in dollars per share)		72.23	$ 66.13	$ 51.36
Vested (in dollars per share)		64.85
Forfeited or expired (in dollars per share)		63.68
Nonvested balance end of period (in dollars per share)		$ 64.61	$ 62.13
Vesting period		5 years
Forecast [Member]
Weighted Average Grant Date Fair Value Per Share [Abstract]
Vesting period	5 years
Subsequent Event [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (in shares)	164,793

Stock Award Plans, Director Pla

Stock Award Plans, Director Plan Stock Option Activity (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
2005 Stock and Incentive Plan [Member]
Stock Award Plan Information [Abstract]
Shares available for future grants (in shares)	2,045,694
Director Plan [Member]
Stock Award Plan Information [Abstract]
Shares available for future grants (in shares)	369,360
Director Plan [Member] \| Employee Stock Option
Stock Award Plan Information [Abstract]
Term of grant	10 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at Period Start (in shares)	56,480
Granted (in shares)	3,865
Exercised (in shares)	0
Expired (in shares)	(30,000)
Outstanding at Period End (in shares)	30,345
Weighted Average Exercise Price [Abstract]
Outstanding at Period Start (in dollars per share) \| $ / shares	$ 86.19
Granted (in dollars per share) \| $ / shares	72.83
Exercised (in dollars per share) \| $ / shares	0
Expired (in dollars per share) \| $ / shares	80.04
Outstanding at Period End (in dollars per share) \| $ / shares	$ 90.57
Director Plan [Member] \| Restricted Stock [Member]
Stock Award Plan Information [Abstract]
Vesting period	6 months

Stock Award Plans, Director P_2

Stock Award Plans, Director Plan Outstanding and Exercisable Options (Details) - Director Plan [Member] - Employee Stock Option [Member] $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
First Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	$ 70.65
Share-Based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit	$ 73.57
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	7,053
Weighted Average Remaining Contractual Life	6 years 7 months 6 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 71.85
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	6,278
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 71.75
Second Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	84.9
Share-Based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit	$ 85.3
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	5,292
Weighted Average Remaining Contractual Life	4 years 9 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 85.1
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	5,292
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 85.1
Third Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	$ 99.52
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	18,000
Weighted Average Remaining Contractual Life	3 months 18 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 99.52
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	18,000
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 99.52
Full Exercise Price Range [Member]
Outstanding and Exercisable Stock options [Abstract]
Range of Exercise Prices, lower limit (in dollars per share)	70.65
Share-Based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit	$ 99.52
Options Outstanding [Abstract]
Number Outstanding (in shares) \| shares	30,345
Weighted Average Remaining Contractual Life	2 years 7 months 6 days
Weighted Average Exercise Price, Options Outstanding (in dollars per share)	$ 90.57
Aggregate Intrinsic Value, Options Outstanding \| $	$ 47
Options Exercisable [Abstract]
Number Exercisable (in shares) \| shares	29,570
Weighted Average Exercise Price, Options Exercisable (in dollars per share)	$ 91.04
Aggregate Intrinsic Value, Options Exercisable \| $	$ 42

Stock Award Plans, Director P_3

Stock Award Plans, Director Plan Restricted Stock Award Activity (Details) - Director Plan [Member] - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested balance beginning of period (in shares)	1,698
Granted (in shares)	31,526
Vested (in shares)	(32,604)
Nonvested balance end of period (in shares)	620	1,698
Weighted Average Grant Date Fair Value Per Share [Abstract]
Nonvested balance beginning of period (in dollars per share)	$ 65.36
Granted (in dollars per share)	72.67	$ 64.61	$ 65.13
Vested (in dollars per share)	72.29
Nonvested balance end of period (in dollars per share)	$ 72.65	$ 65.36

Stock Award Plans, All Plans Op

Stock Award Plans, All Plans Options and Restricted Stock Award Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Plans Combined Disclosure [Abstract]
Intrinsic value of stock options exercised	$ 1,500,000	$ 400,000	$ 100,000
Intrinsic value of restricted stock vesting	2,500,000	3,200,000	5,300,000
Tax benefit from restricted stock vesting	600,000	800,000	1,500,000
Employee Stock Award Plan [Member]
Share-based Compensation Plans Combined Disclosure [Abstract]
Intrinsic value of restricted stock vesting	10,900,000	9,500,000	4,400,000
Tax benefit from restricted stock vesting	$ 2,600,000	$ 2,400,000	$ 1,200,000
Fair value of stock options granted	0	0	0
Director Plan [Member]
Share-based Compensation Plans Combined Disclosure [Abstract]
Fair value of stock options granted (in dollars per share)	$ 32.33
Fair value of stock options granted	$ 100,000
Employee Stock Option
Fair Value Assumptions [Abstract]
Dividend yield	0%
Average risk-free interest rate	3.70%
Stock price volatility	35%
Estimated option term	7 years
Restricted Stock [Member]
Share-based Compensation Plans Combined Disclosure [Abstract]
Unrecognized compensation cost related to unvested awards	$ 45,000
Weighted average period of recognition in years	2 months 12 days
Restricted Stock [Member] \| Director Plan [Member]
Share-based Compensation Plans Combined Disclosure [Abstract]
Vesting (in shares)	32,604
RSUs [Member]
Share-based Compensation Plans Combined Disclosure [Abstract]
Unrecognized compensation cost related to unvested awards	$ 15,300,000
Weighted average period of recognition in years	2 years 8 months 12 days
RSUs [Member] \| Employee Stock Award Plan [Member]
Share-based Compensation Plans Combined Disclosure [Abstract]
Vesting (in shares)	161,550

Taxes on Income, Earnings (Loss

Taxes on Income, Earnings (Loss) Before Taxes (Details) - USD ($) $ in Thousands			12 Months Ended
	Nov. 13, 2021	Nov. 12, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Apr. 30, 2023
Earnings (loss) before taxes on income [Abstract]
Earnings (loss) before taxes on income			$ 294,125	$ 164,975	$ (290,601)
U.S. Federal [Abstract]
Current			(41)	513	(460)
Deferred			61,205	34,980	(48,843)
Federal Income Tax Expense (Benefit), Continuing Operations			61,164	35,493	(49,303)
U.S. State [Abstract]
Current			5,498	3,793	1,560
Deferred			4,093	2,802	4,424
State and Local Income Tax Expense (Benefit), Continuing Operations			9,591	6,595	5,984
Foreign [Abstract]
Current			465	126	(511)
Foreign Income Tax Expense (Benefit), Continuing Operations			465	126	(511)
Consolidated [Abstract]
Current			5,922	4,432	589
Deferred			65,298	37,782	(44,419)
Total Provision (benefit) for taxes on income			$ 71,220	$ 42,214	$ (43,830)
Income Taxes [Abstract]
Effective income tax rate			21%	21%	21%
Tax refund amount					$ 119,500	$ 70,400
Income tax receivable				$ 70,400
State and local taxes, net of federal benefit			2.60%	3.10%	(1.70%)
United States [Member]
Earnings (loss) before taxes on income [Abstract]
Earnings (loss) before taxes on income			$ 293,011	$ 164,590	$ (290,181)
Foreign [Member]
Earnings (loss) before taxes on income [Abstract]
Earnings (loss) before taxes on income			$ 1,114	$ 385	$ (420)
Louisiana [Member]
Income Taxes [Abstract]
Effective income tax rate	8%	7.50%
State and local taxes, net of federal benefit	7.50%	6.30%
One-time deferred tax provision	$ 5,700

Taxes on Income, Schedule of Ef

Taxes on Income, Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Company's provision for taxes on income varied from the statutory federal income tax rate [Abstract]
United States income tax statutory rate	21%	21%	21%
State and local taxes, net of federal benefit	2.60%	3.10%	(1.70%)
Other - net	0.60%	1.50%	(4.20%)
Effective income tax rate	24.20%	25.60%	15.10%

Taxes on Income, Schedule of De

Taxes on Income, Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets [Abstract]
Allowance for doubtful accounts		$ 1,549	$ 1,556
Inventory		10,500	11,679
Insurance accruals		6,077	4,856
Deferred compensation		11,441	7,703
Unrealized gain on defined benefit plans		(9,982)	(5,532)
Goodwill and other intangibles		39,719	52,847
Operating loss carryforwards		52,082	79,699
Retirement benefits		3,548	5,472
Other		13,467	9,962
Deferred tax assets, gross		128,401	168,242
Valuation allowances		(22,073)	(19,960)
Deferred tax assets, net of valuation allowance		106,328	148,282
Deferred tax liabilities [Abstract]
Property		(695,233)	(671,830)
Deferred state taxes		(90,457)	(87,445)
Other		(17,195)	(14,891)
Deferred tax liabilities		(802,885)	(774,166)
Net deferred tax liabilities		(696,557)	(625,884)
Operating Loss Carryforward [Abstract]
Federal operating loss deferred tax assets		19,800	47,900
Deferred Tax Assets, State Taxes		27,200	26,600
Valuation allowance for state deferred tax assets		17,000	$ 14,800
Unrecognized tax benefits including interest and penalties		800
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		$ 700
Maximum [Member]
Operating Loss Carryforward [Abstract]
Expiration dates, operating loss carryforwards		Dec. 31, 2043
Minimum [Member]
Operating Loss Carryforward [Abstract]
Expiration dates, operating loss carryforwards		Dec. 31, 2037
Canada [Member]
Operating Loss Carryforward [Abstract]
Operating loss carryforwards		$ 5,100
Expiration dates, operating loss carryforwards		Dec. 31, 2030
Internal Revenue Service (IRS) [Member]
Open Tax Year [Abstract]
Years open to audit under the statute of limitations	2013 2014 2015 2016 2017 2018 2019 2020
State and Local Jurisdiction [Member]
Open Tax Year [Abstract]
Years open to audit under the statute of limitations	2017 2018 2019 2020 2021 2022

Taxes on Income, Reconciliation

Taxes on Income, Reconciliation of Liability for Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 662	$ 737	$ 783
Additions based on tax positions related to the current year	0	13	13
Additions for tax positions of prior years	0	66	281
Reductions for tax positions of prior years	(14)	(154)	(340)
Balance at end of year	648	662	$ 737
Accrued liabilities for payment of interest and penalties	$ 200	$ 200

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Income (Loss) Attributable to Parent [Abstract]
Net earnings (loss) attributable to Kirby	$ 222,935	$ 122,291	$ (246,954)
Undistributed earnings allocated to restricted shares	(62)	(33)	0
Earnings (loss) available to Kirby common stockholders - basic	222,873	122,258	(246,954)
Undistributed earnings allocated to restricted shares	62	33	0
Undistributed earnings allocated to restricted shares	(62)	(33)	0
Earnings (loss) available to Kirby common stockholders - diluted	$ 222,873	$ 122,258	$ (246,954)
Shares outstanding [Abstract]
Weighted average common stock issued and outstanding (in shares)	59,548,000	60,055,000	60,099,000
Weighted average unvested restricted stock (in shares)	(17,000)	(17,000)	(46,000)
Weighted Average Number of Shares Outstanding, Basic (in Shares)	59,531,000	60,038,000	60,053,000
Dilutive effect of stock options and restricted stock units (in shares)	326,000	291,000	0
Weighted Average Number of Shares Outstanding, Diluted (in Shares)	59,857,000	60,329,000	60,053,000
Net earnings (loss) per share basic attributable to Kirby common stockholders:
Basic (in dollars per share)	$ 3.74	$ 2.04	$ (4.11)
Net earnings (loss) per share diluted attributable to Kirby common stockholders:
Diluted (in dollars per share)	$ 3.72	$ 2.03	$ (4.11)
Antidilutive securities excluded from computation of earnings per share (in shares)	33,000	381,000	567,000
Restricted Stock Units (RSUs) [Member]
Net earnings (loss) per share diluted attributable to Kirby common stockholders:
Antidilutive securities excluded from computation of earnings per share (in shares)	0	0	7,000

Schedule of Inventories, Net (D

Schedule of Inventories, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Inventory, Net [Abstract]
Inventory, Finished Goods, Gross	$ 351,050	$ 358,702
Inventory, Work in Process, Gross	103,339	103,146
Inventories - net	$ 454,389	$ 461,848

Retirement Plans, Information A

Retirement Plans, Information About Plan Assets and Asset Allocation (Details) - USD ($)		12 Months Ended
		Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
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
Fair Value, Inputs, Level 3 [Member]
Information about Plan Assets [Abstract]
Fair value of plan assets		$ 0		$ 0
Cash and Equity Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Information about Plan Assets [Abstract]
Fair value of plan assets				4,800
Pension Plan [Member]
Information about Plan Assets [Abstract]
Pension contributions		8,174,000		906,000
Fair value of plan assets		$ 375,917,000		$ 341,061,000		$ 430,821,000
Expected long-term rate of return on plan assets		6.75%		6.75%		6.75%
Contribution percentage to defined contribution plan		115%
Discount rate		5.50%	[1]	3%
Asset Allocation Among Asset Categories [Abstract]
Asset allocations		100%		100%
Pension Plan [Member] \| Minimum [Member]
Information about Plan Assets [Abstract]
Discount rate				3%	[1]	2.80%
Pension Plan [Member] \| Maximum [Member]
Information about Plan Assets [Abstract]
Discount rate				3.10%	[1]	2.90%
Pension Plan [Member] \| U.S. Equity Securities [Member]
Asset Allocation Among Asset Categories [Abstract]
Asset allocations		51%		50%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		50%
Pension Plan [Member] \| U.S. Equity Securities [Member] \| Minimum [Member]
Asset Allocation Among Asset Categories [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		45%
Pension Plan [Member] \| U.S. Equity Securities [Member] \| Maximum [Member]
Asset Allocation Among Asset Categories [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		55%
Pension Plan [Member] \| International Equity Securities [Member]
Asset Allocation Among Asset Categories [Abstract]
Asset allocations		20%		20%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		20%
Pension Plan [Member] \| International Equity Securities [Member] \| Minimum [Member]
Asset Allocation Among Asset Categories [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		12%
Pension Plan [Member] \| International Equity Securities [Member] \| Maximum [Member]
Asset Allocation Among Asset Categories [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		28%
Pension Plan [Member] \| Debt Securities [Member]
Asset Allocation Among Asset Categories [Abstract]
Asset allocations		29%		30%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		30%
Pension Plan [Member] \| Debt Securities [Member] \| Minimum [Member]
Asset Allocation Among Asset Categories [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		20%
Pension Plan [Member] \| Debt Securities [Member] \| Maximum [Member]
Asset Allocation Among Asset Categories [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		40%
Pension Plan [Member] \| Cash and Cash Equivalents [Member]
Asset Allocation Among Asset Categories [Abstract]
Asset allocations		0%		0%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		0%
Pension Plan [Member] \| Cash and Cash Equivalents [Member] \| Minimum [Member]
Asset Allocation Among Asset Categories [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		0%
Pension Plan [Member] \| Cash and Cash Equivalents [Member] \| Maximum [Member]
Asset Allocation Among Asset Categories [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage		0%
SERP [Member]
Information about Plan Assets [Abstract]
Pension contributions		$ 153,000		$ 155,000
Fair value of plan assets		$ 0		$ 0		$ 0
Expected long-term rate of return on plan assets		0%		0%		0%
Discount rate	[1]	5.50%		3%		2.80%
Other Postretirement Benefits [Member]
Information about Plan Assets [Abstract]
Pension contributions		$ 104,000		$ 109,000
Fair value of plan assets		$ 0		$ 0		$ 0
Pension plan defined benefit plan cost increase limit percentage		4%
Discount rate		5.50%		3%		2.80%
Seafarers Pension Trust [Member]
Information about Plan Assets [Abstract]
Pension contributions		$ 400,000		$ 500,000
Contribution percentage to defined contribution plan				100%
Central Pension Fund of the International Union of Operating [Member]
Information about Plan Assets [Abstract]
Pension contributions		600,000		$ 700,000
Contribution percentage to defined contribution plan				107%
Higman Pension Plan [Member]
Information about Plan Assets [Abstract]
Pension contributions		$ 8,200,000		$ 900,000		$ 500
Discount rate				3.10%

[1] The 2023 discount rate for benefit cost is 5.5% for both the Kirby Pension Plan and the Higman Pension Plan. The 2022 discount rate for benefit cost is 3.0 % for the Kirby Pension Plan and 3.1 % for the Higman Pension Plan.

Retirement Plans, Schedule of C

Retirement Plans, Schedule of Change in Benefit Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 339,509	$ 495,272
Service cost	3,695	6,538	$ 7,961
Interest cost	18,356	14,779	14,239
Actuarial (gain) loss	13,241	(158,816)
Gross benefits paid	(32,052)	(12,665)
Settlements	0	(5,599)
Benefit obligation at end of year	342,749	339,509	495,272
Accumulated benefit obligation at end of year	326,987	325,274
SERP [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	833	1,033
Service cost	0	0	0
Interest cost	43	29	31
Actuarial (gain) loss	91	(74)
Gross benefits paid	(153)	(155)
Settlements	0	0
Benefit obligation at end of year	814	833	1,033
Accumulated benefit obligation at end of year	814	833
Other Postretirement Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	432	582
Service cost	0	0
Interest cost	22	17	17
Actuarial (gain) loss	65	(58)
Gross benefits paid	(104)	(109)
Settlements	0	0
Benefit obligation at end of year	415	432	$ 582
Accumulated benefit obligation at end of year	$ 415	$ 432

Retirement Plans, Weighted-Aver

Retirement Plans, Weighted-Average Assumption Used to Determine Benefit Obligation (Details)		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022
Pension Plan [Member]
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]
Discount rate		5.10%	5.50%	[1]
Health care cost trend rate [Abstract]
Initial rate		0%	0%
Ultimate rate		0%	0%
Pension Plan [Member] \| Minimum [Member]
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]
Discount rate	[1]	5.10%
Pension Plan [Member] \| Maximum [Member]
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]
Discount rate	[1]	5.20%
SERP [Member]
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]
Discount rate	[1]	5.10%	5.50%
Rate of compensation increase		0%	0%
Health care cost trend rate [Abstract]
Initial rate		0%	0%
Ultimate rate		0%	0%
Other Postretirement Benefits [Member]
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]
Discount rate	[1]	5.10%	5.50%
Rate of compensation increase		0%	0%
Health care cost trend rate [Abstract]
Initial rate		6.25%	6.50%
Ultimate rate		5%	5%
Years to ultimate		2029	2029
Higman Pension Plan [Member]
Weighted-average assumption used to determine benefit obligation at end of year [Abstract]
Discount rate		5.20%	5.50%

[1] The 2023 discount rate was 5.1 % for the Kirby Pension Plan and 5.2 % for the Higman Pension Plan. The 2022 discount rate was 5.5 % for both the Kirby Pension Plan and the Higman Pension Plan.

Retirement Plans, Summary of Ch

Retirement Plans, Summary of Change in Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pension Plan [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 341,061	$ 430,821
Actual return on plan assets	58,734	(72,402)
Employer contribution	8,174	906
Gross benefits paid	(32,052)	(12,665)
Settlements	0	(5,599)
Fair value of plan assets at end of year	375,917	341,061
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	153	155
Gross benefits paid	(153)	(155)
Settlements	0	0
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	104	109
Gross benefits paid	(104)	(109)
Settlements	0	0
Fair value of plan assets at end of year	$ 0	$ 0

Retirement Plans, Summary of Fu

Retirement Plans, Summary of Funded Status at End of Year (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Plan [Member]
Funded status at end of year [Abstract]
Fair value of plan assets	$ 375,917	$ 341,061	$ 430,821
Benefit obligations	(342,749)	(339,509)	(495,272)
Funded status and amount recognized at end of year	33,168	1,552
SERP [Member]
Funded status at end of year [Abstract]
Fair value of plan assets	0	0	0
Benefit obligations	(814)	(833)	(1,033)
Funded status and amount recognized at end of year	(814)	(833)
Other Postretirement Benefits [Member]
Funded status at end of year [Abstract]
Fair value of plan assets	0	0	0
Benefit obligations	(415)	(432)	$ (582)
Funded status and amount recognized at end of year	$ (415)	$ (432)

Retirement Plans, Amounts Recog

Retirement Plans, Amounts Recognized in Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Pension Plan [Member]
Amounts recognized in the consolidated balance sheets [Abstract]
Noncurrent asset	$ 42,698	$ 18,695
Current liability	0	0
Long-term liability	(9,530)	(17,143)
SERP [Member]
Amounts recognized in the consolidated balance sheets [Abstract]
Noncurrent asset	0	0
Current liability	(106)	(106)
Long-term liability	(708)	(727)
Other Postretirement Benefits [Member]
Amounts recognized in the consolidated balance sheets [Abstract]
Noncurrent asset	0	0
Current liability	(46)	(49)
Long-term liability	$ (369)	$ (383)

Retirement Plans, Amounts Rec_2

Retirement Plans, Amounts Recognized in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Pension Plan [Member]
Amounts recognized in accumulated other comprehensive income [Abstract]
Net actuarial (gain) loss	$ (48,033)	$ (25,449)
Prior service cost (credit)	0	0
Accumulated other compensation income	(48,033)	(25,449)
SERP [Member]
Amounts recognized in accumulated other comprehensive income [Abstract]
Net actuarial (gain) loss	391	324
Prior service cost (credit)	0	0
Accumulated other compensation income	391	324
Other Postretirement Benefits [Member]
Amounts recognized in accumulated other comprehensive income [Abstract]
Net actuarial (gain) loss	(1,890)	(2,299)
Prior service cost (credit)	0	0
Accumulated other compensation income	$ (1,890)	$ (2,299)

Retirement Plans, Expected Empl

Retirement Plans, Expected Employer Contribution and Benefit Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Pension Plan [Member]
Expected employer contributions [Abstract]
First year	$ 1,770	$ 8,374
Expected benefit payments (gross) [Abstract]
Year one	16,696	16,312
Year two	17,513	16,899
Year three	18,169	17,808
Year four	19,096	18,650
Year five	19,860	19,707
Next five years	108,717	110,417
SERP [Member]
Expected employer contributions [Abstract]
First year	0	0
Expected benefit payments (gross) [Abstract]
Year one	108	108
Year two	103	104
Year three	98	99
Year four	93	94
Year five	88	90
Next five years	337	359
Other Postretirement Benefits [Member]
Expected employer contributions [Abstract]
First year	0	0
Expected benefit payments (gross) [Abstract]
Year one	47	50
Year two	46	49
Year three	44	47
Year four	43	45
Year five	41	43
Next five years	$ 167	$ 176

Retirement Plans, Components of

Retirement Plans, Components of Net Periodic Benefit Cost, Pension Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Components of net periodic benefit cost [Abstract]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax
Other changes in plan assets and benefit obligations recognized in other comprehensive income [Abstract]
Recognition of actuarial loss	$ (22,438)	$ (58,147)	$ (44,491)
Pension Plan [Member]
Components of net periodic benefit cost [Abstract]
Service cost	3,695	6,538	7,961
Interest cost	18,356	14,779	14,239
Expected return on plan assets	(22,910)	(28,399)	(26,244)
Amortization of actuarial loss	0	34	4,193
Net periodic benefit cost	(859)	(7,048)	(149)
Other changes in plan assets and benefit obligations recognized in other comprehensive income [Abstract]
Current year actuarial (gain) loss	(22,583)	(58,015)	(44,583)
Recognition of actuarial loss	0	(34)	(4,193)
Total recognized in other comprehensive income	(22,583)	(58,049)	(48,776)
Total recognized in net periodic benefit cost and other comprehensive income	(23,442)	(65,097)	(48,627)
SERP [Member]
Components of net periodic benefit cost [Abstract]
Service cost	0	0	0
Interest cost	43	29	31
Expected return on plan assets	0	0	0
Amortization of actuarial loss	23	30	40
Net periodic benefit cost	66	59	71
Other changes in plan assets and benefit obligations recognized in other comprehensive income [Abstract]
Current year actuarial (gain) loss	91	(74)	(12)
Recognition of actuarial loss	(23)	(30)	(40)
Total recognized in other comprehensive income	68	(104)	(52)
Total recognized in net periodic benefit cost and other comprehensive income	$ 134	$ (45)	$ 19

Retirement Plans, Weighted Aver

Retirement Plans, Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost, Pension Benefits (Details)		12 Months Ended
		Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
Pension Benefits [Member]
Weighted average assumptions used to determine net periodic benefit cost [Abstract]
Discount rate		5.50%	[1]	3%
Expected long-term rate of return on plan assets		6.75%		6.75%		6.75%
Pension Benefits [Member] \| Maximum [Member]
Weighted average assumptions used to determine net periodic benefit cost [Abstract]
Discount rate				3.10%	[1]	2.90%
Pension Benefits [Member] \| Minimum [Member]
Weighted average assumptions used to determine net periodic benefit cost [Abstract]
Discount rate				3%	[1]	2.80%
SERP [Member]
Weighted average assumptions used to determine net periodic benefit cost [Abstract]
Discount rate	[1]	5.50%		3%		2.80%
Expected long-term rate of return on plan assets		0%		0%		0%
Rate of compensation increase		0%		0%		0%
Higman Pension Plan [Member]
Weighted average assumptions used to determine net periodic benefit cost [Abstract]
Discount rate				3.10%

[1] The 2023 discount rate for benefit cost is 5.5% for both the Kirby Pension Plan and the Higman Pension Plan. The 2022 discount rate for benefit cost is 3.0 % for the Kirby Pension Plan and 3.1 % for the Higman Pension Plan.

Retirement Plans, Components _2

Retirement Plans, Components of Net Periodic Benefit Cost, Other Postretirement Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Recognition of actuarial gain	$ (22,438)	$ (58,147)	$ (44,491)
Other Postretirement Benefits [Member]
Components of net periodic benefit cost [Abstract]
Interest cost	22	17	17
Amortization of actuarial gain	(344)	(394)	(451)
Net periodic benefit cost	(322)	(377)	(434)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract]
Current year actuarial loss (gain)	65	(58)	104
Recognition of actuarial gain	344	394	451
Total recognized in other comprehensive income	409	336	555
Total recognized in net periodic benefit cost and other comprehensive income	$ 87	$ (41)	$ 121

Retirement Plans, Weighted Av_2

Retirement Plans, Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost, Other Postretirement Benefits (Details) - Other Postretirement Benefits [Member]	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Weighted average assumptions used to determine net periodic benefit cost [Abstract]
Discount rate	5.50%	3%	2.80%
Health care cost trend rate [Abstract]
Initial rate	6.50%	6.25%	6.50%
Ultimate rate	5%	5%	5%
Years to ultimate	2029	2027	2025

Retirement Plans, Multiemployer

Retirement Plans, Multiemployer Pension Plan and Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Plans [Abstract]
Aggregate contributions to the plans	$ 26.9	$ 27.9	$ 25.9
Seafarers Pension Trust [Member]
Retirement Plans [Abstract]
Pension contributions	0.4	$ 0.5
Contribution percentage to defined contribution plan		100%
Maximum contribution limit		5%
CPF [Member]
Retirement Plans [Abstract]
Pension contributions	$ 0.6	$ 0.7
Contribution percentage to defined contribution plan		107%

Other Comprehensive Income (L_3

Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax [Abstract]
Amortization of net actuarial (gain) loss, Gross Amount	$ (321)	$ (330)	$ 3,782
Amortization of net actuarial (gain) loss, Income Tax (Provision) Benefit	78	81	(952)
Amortization of net actuarial (gain) loss, Net Amount	(243)	(249)	2,830
Actuarial gain , Gross Amount	22,438	58,147	44,491
Actuarial gain , Income Tax (Provision) Benefit	(5,467)	(14,030)	(10,774)
Actuarial gain , Net Amount	16,971	44,117	33,717
Foreign currency translation, Gross Amount	1,425	(1,049)	(1,061)
Foreign currency translation, Income Tax (Provision) Benefit	0	0	0
Foreign currency translation, Net Amount	1,425	(1,049)	(1,061)
Total other comprehensive income (loss), Gross Amount	23,542	56,768	47,212
Total other comprehensive income (loss), Income Tax (Provision) Benefit	(5,389)	(13,949)	(11,726)
Total other comprehensive income , net of taxes	$ 18,153	$ 42,819	$ 35,486

Contingencies and Commitments (

Contingencies and Commitments (Details)	12 Months Ended
Contingencies and Commitments (Details)	Dec. 31, 2023 Bargeslip Company Spill
Portland Harbor Superfund Site [Member]
Loss Contingencies [Line Items]
Number of other companies also named as Potentially Responsible Parties ("PRPs") \| Company	250
Number of spills \| Spill	4
SBA Shipyard Site [Member]
Loss Contingencies [Line Items]
Number of barge slips \| Bargeslip	3

Contingencies and Commitments,

Contingencies and Commitments, Certain Significant Risks and Uncertainties (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Loss Contingencies [Line Items]
Issued guaranties	$ 26.7
Maximum [Member]
Loss Contingencies [Line Items]
Guarantor obligations, expiration period	2 years
Performance Bonds [Member]
Loss Contingencies [Line Items]
Issued guaranties	$ 14.6
Letters Of Credit [Member]
Loss Contingencies [Line Items]
Issued guaranties	$ 12.1

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
ABS [Member]
Related Party [Abstract]
Related party expenses	$ 1.5	$ 1.3	$ 1.6
UK Protection & Indemnity Association [Member]
Related Party [Abstract]
Related party expenses	3.6	3.4	3.2
Signal Member
Related Party [Abstract]
Related party expenses	0.7	0.5	0.6
Strasburger & Price, LLP Member
Related Party [Abstract]
Legal services	0.9	1	2.9
W. Sean O'Neil Attorney Member
Related Party [Abstract]
Legal services	0.1	$ 0.1	$ 0.1
Mansfield Service Partners Member
Related Party [Abstract]
Related party expenses	$ 29.4