ArcBest (ARCB) 10-K 23 Feb 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2023	Feb. 19, 2024	Jun. 30, 2023
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	0-19969
Entity Registrant Name	ARCBEST CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	71-0673405
Entity Address, Address Line One	8401 McClure Drive
Entity Address, City or Town	Fort Smith
Entity Address, State or Province	AR
Entity Address, Postal Zip Code	72916
City Area Code	479
Local Phone Number	785-6000
Title of 12(b) Security	Common Stock
Trading Symbol	ARCB
Security Exchange Name	NASDAQ
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
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 2,326,818,530
Entity Common Stock, Shares Outstanding		23,520,701
Auditor Name	Ernst & Young LLP
Auditor Location	Tulsa, Oklahoma
Auditor Firm ID	42
Entity Central Index Key	0000894405
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
CURRENT ASSETS
Cash and cash equivalents	$ 262,226	$ 158,264
Short-term investments	67,842	167,662
Accounts receivable, less allowances (2023 - $10,346; 2022 - $13,892)	430,122	517,494
Other accounts receivable, less allowances (2023 - $731; 2022 - $713)	52,124	11,016
Prepaid expenses	37,034	39,484
Prepaid and refundable income taxes	24,319	19,239
Current assets of discontinued operations		64,736
Other	11,116	11,888
TOTAL CURRENT ASSETS	884,783	989,783
PROPERTY, PLANT AND EQUIPMENT
Land and structures	460,068	401,840
Revenue equipment	1,126,055	1,038,832
Service, office, and other equipment	319,466	298,234
Software	173,354	167,164
Leasehold improvements	24,429	23,466
TOTAL PROPERTY, PLANT AND EQUIPMENT, Gross	2,103,372	1,929,536
Less allowances for depreciation and amortization	1,188,548	1,129,366
PROPERTY, PLANT AND EQUIPMENT, net	914,824	800,170
GOODWILL	304,753	304,753
INTANGIBLE ASSETS, net	101,150	113,733
OPERATING RIGHT-OF-USE ASSETS	169,999	166,515
DEFERRED INCOME TAXES	8,140	6,342
LONG-TERM ASSETS OF DISCONTINUED OPERATIONS		11,097
OTHER LONG-TERM ASSETS	101,445	101,893
TOTAL ASSETS	2,485,094	2,494,286
CURRENT LIABILITIES
Accounts payable	214,004	269,854
Income taxes payable	10,410	16,017
Accrued expenses	378,029	338,457
Current portion of long-term debt	66,948	66,252
Current portion of operating lease liabilities	32,172	26,225
Current liabilities of discontinued operations		51,665
TOTAL CURRENT LIABILITIES	701,563	768,470
LONG-TERM DEBT, less current portion	161,990	198,371
OPERATING LEASE LIABILITIES, less current portion	176,621	147,828
POSTRETIREMENT LIABILITIES, less current portion	13,319	12,196
LONG-TERM LIABILITIES OF DISCONTINUED OPERATIONS		781
CONTINGENT CONSIDERATION	92,900	112,000
OTHER LONG-TERM LIABILITIES	40,553	42,745
DEFERRED INCOME TAXES	55,785	60,494
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2023: 30,024,125 shares; 2022: 29,758,716 shares	300	298
Additional paid-in capital	340,961	339,582
Retained earnings	1,272,584	1,088,693
Treasury stock, at cost, 2023: 6,460,137 shares; 2022: 5,529,383 shares	(375,806)	(284,275)
Accumulated other comprehensive income	4,324	7,103
TOTAL STOCKHOLDERS' EQUITY	1,242,363	1,151,401
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 2,485,094	$ 2,494,286

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowances (in dollars)	$ 10,346	$ 13,892
Other accounts receivable, allowances (in dollars)	$ 731	$ 713
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares	70,000,000	70,000,000
Common stock, issued shares	30,024,125	29,758,716
Treasury stock, at cost, shares	6,460,137	5,529,383

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CONSOLIDATED STATEMENTS OF OPERATIONS
REVENUES	$ 4,427,443	$ 5,029,008	$ 3,766,185
OPERATING EXPENSES	4,254,824	4,634,482	3,489,207
OPERATING INCOME	172,619	394,526	276,978
OTHER INCOME (COSTS)
Interest and dividend income	14,728	3,873	1,226
Interest and other related financing costs	(9,094)	(7,726)	(8,914)
Other, net	8,662	(2,370)	3,797
TOTAL OTHER INCOME (COSTS)	14,296	(6,223)	(3,891)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	186,915	388,303	273,087
INCOME TAX PROVISION	44,751	93,655	62,628
NET INCOME FROM CONTINUING OPERATIONS	142,164	294,648	210,459
INCOME FROM DISCONTINUED OPERATIONS, NET OF TAX	53,269	3,561	3,062
NET INCOME	$ 195,433	$ 298,209	$ 213,521
BASIC EARNINGS PER COMMON SHARE
Continuing operations (in dollars per share)	$ 5.92	$ 11.98	$ 8.26
Discontinued operations (in dollars per share)	2.22	0.14	0.12
BASIC EARNINGS PER COMMON SHARE (in dollars per share)	8.14	12.13	8.38
DILUTED EARNINGS PER COMMON SHARE
Continuing operations (in dollars per share)	5.77	11.55	7.86
Discontinued operations (in dollars per share)	2.16	0.14	0.11
DILUTED EARNINGS PER COMMON SHARE (in dollars per share)	$ 7.93	$ 11.69	$ 7.98
AVERAGE COMMON SHARES OUTSTANDING
Basic (in shares)	24,018,801	24,585,205	25,471,939
Diluted (in shares)	24,634,617	25,504,508	26,772,126

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net Income (Loss)	$ 195,433	$ 298,209	$ 213,521
Postretirement benefit plans:
Net actuarial gain (loss), net of tax of: (2023 - $294; 2022 - $1,144; 2021 - $451)	(847)	3,298	1,300
Amortization of unrecognized net periodic benefit cost (credit), net of tax of: (2023 - $342; 2022 - $195, 2021 - $139)
Net actuarial gain	(988)	(562)	(400)
Interest rate swap and foreign currency translation:
Change in unrealized gain (loss) on interest rate swap, net of tax of: (2023 - $475; 2022 - $812, 2021 - $534)	(1,341)	2,295	1,507
Change in foreign currency translation, net of tax of: (2023 - $141; 2022 - $576, 2021 - $36)	397	(1,627)	102
OTHER COMPREHENSIVE INCOME (LOSS), net of tax	(2,779)	3,404	2,509
TOTAL COMPREHENSIVE INCOME	$ 192,654	$ 301,613	$ 216,030

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net actuarial gain, tax	$ (294)	$ 1,144	$ 451
Amortization of unrecognized net periodic benefit cost, tax	(342)	(195)	(139)
Change in unrealized gain (loss) on interest rate swap, tax	(475)	812	534
Change in foreign currency translation, tax	$ 141	$ (576)	$ 36

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income	Total
Balances at Dec. 31, 2020	$ 290	$ 342,354	$ 595,932	$ (111,173)	$ 1,190	$ 828,593
Balances (in shares) at Dec. 31, 2020	29,045,000
Balances, Treasury stock (in shares) at Dec. 31, 2020				3,657,000
Increase (Decrease) in Stockholders' Equity
Net income			213,521			213,521
Other comprehensive income (loss), net of tax					2,509	2,509
Issuance of common stock under share-based compensation plans	$ 4	(4)
Issuance of common stock under share-based compensation plans (in shares)	315,000
Shares withheld for employee tax remittance on share-based compensation		(10,743)				(10,743)
Share-based compensation expense		11,426				11,426
Purchase of treasury stock				$ (83,100)		(83,100)
Purchase of treasury stock (in shares)				836,000
Forward contract for accelerated share repurchase		(25,000)				(25,000)
Dividends declared on common stock			(8,139)			(8,139)
Balances at Dec. 31, 2021	$ 294	318,033	801,314	$ (194,273)	3,699	929,067
Balances (in shares) at Dec. 31, 2021	29,360,000
Balances, Treasury stock (in shares) at Dec. 31, 2021				4,493,000
Increase (Decrease) in Stockholders' Equity
Net income			298,209			298,209
Other comprehensive income (loss), net of tax					3,404	3,404
Issuance of common stock under share-based compensation plans	$ 4	(4)
Issuance of common stock under share-based compensation plans (in shares)	399,000
Shares withheld for employee tax remittance on share-based compensation		(16,222)				(16,222)
Share-based compensation expense		12,775				12,775
Purchase of treasury stock				$ (65,002)		(65,002)
Purchase of treasury stock (in shares)				822,000
Forward contract for accelerated share repurchase		25,000		$ (25,000)
Forward contract for accelerated share repurchase (in shares)				214,000
Dividends declared on common stock			(10,830)			(10,830)
Balances at Dec. 31, 2022	$ 298	339,582	1,088,693	$ (284,275)	7,103	$ 1,151,401
Balances (in shares) at Dec. 31, 2022	29,759,000
Balances, Treasury stock (in shares) at Dec. 31, 2022				5,529,000		5,529,383
Increase (Decrease) in Stockholders' Equity
Net income			195,433			$ 195,433
Other comprehensive income (loss), net of tax					(2,779)	(2,779)
Issuance of common stock under share-based compensation plans	$ 2	(2)
Issuance of common stock under share-based compensation plans (in shares)	265,000
Shares withheld for employee tax remittance on share-based compensation		(10,311)				(10,311)
Share-based compensation expense		11,692				11,692
Purchase of treasury stock				$ (91,531)		(91,531)
Purchase of treasury stock (in shares)				931,000
Dividends declared on common stock			(11,542)			(11,542)
Balances at Dec. 31, 2023	$ 300	$ 340,961	$ 1,272,584	$ (375,806)	$ 4,324	$ 1,242,363
Balances (in shares) at Dec. 31, 2023	30,024,000
Balances, Treasury stock (in shares) at Dec. 31, 2023				6,460,000		6,460,137

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING ACTIVITIES
Net income	$ 195,433	$ 298,209	$ 213,521
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	132,900	127,119	118,864
Amortization of intangibles	12,829	12,920	5,357
Share-based compensation expense	11,438	12,775	11,426
Provision for losses on accounts receivable	3,630	6,955	1,466
Change in deferred income taxes	(5,566)	(6,250)	(7,589)
(Gain) loss on sale of property and equipment	4,797	(11,650)	(8,520)
Gain on sale of subsidiary		(402)	(6,923)
Pre-tax gain on sale of discontinued operations	(70,201)
Lease impairment charges	30,162
Change in fair value of contingent consideration	(19,100)	18,300
Change in fair value of equity investment	(3,739)
Changes in operating assets and liabilities:
Receivables	41,189	(10,349)	(122,782)
Prepaid expenses	2,563	(410)	(1,482)
Other assets	3,830	(2,941)	354
Income taxes	(10,657)	(5,041)	13,136
Operating right-of-use assets and lease liabilities, net	2,920	2,952	623
Accounts payable, accrued expenses, and other liabilities	(10,261)	28,632	106,064
NET CASH PROVIDED BY OPERATING ACTIVITIES	322,167	470,819	323,515
INVESTING ACTIVITIES
Purchases of property, plant and equipment, net of financings	(219,021)	(148,223)	(58,412)
Proceeds from sale of property and equipment	7,763	19,691	13,815
Proceeds from sale of discontinued operations	100,949
Business acquisition, net of cash acquired		2,279	(239,380)
Proceeds from the sale of subsidiary		475	9,013
Purchases of short-term investments	(96,537)	(182,352)	(56,011)
Proceeds from sale of short-term investments	198,120	64,329	73,182
Purchase of long-term investments			(25,350)
Capitalization of internally developed software	(12,977)	(17,282)	(20,061)
NET CASH USED IN INVESTING ACTIVITIES	(21,703)	(261,083)	(303,204)
FINANCING ACTIVITIES
Borrowings under credit facilities		58,000	50,000
Proceeds from notes payable		14,206	3,523
Payments on long-term debt	(69,180)	(115,540)	(171,915)
Net change in book overdrafts	(14,101)	8,356	(1,957)
Deferred financing costs	55	(952)	(314)
Payment of common stock dividends	(11,542)	(10,830)	(8,139)
Purchases of treasury stock	(91,531)	(65,002)	(83,100)
Forward contract for accelerated share repurchase			(25,000)
Payments for tax withheld on share-based compensation	(10,311)	(16,222)	(10,743)
NET CASH USED IN FINANCING ACTIVITIES	(196,610)	(127,984)	(247,645)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	103,854	81,752	(227,334)
CASH AND CASH EQUIVALENTS AT END OF PERIOD	262,226	158,372	76,620
NONCASH INVESTING ACTIVITIES
Equipment financed	33,495	82,425	59,700
Accruals for equipment received	1,727	4,337	1,704
Lease liabilities arising from obtaining right-of-use assets	$ 62,425	$ 87,294	$ 14,671

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CONSOLIDATED STATEMENTS OF CASH FLOWS
Cash and cash equivalents of continuing operations at beginning of period	$ 158,264	$ 76,568	$ 303,872
Cash and cash equivalents of discontinued operations at beginning of period	$ 108	$ 52	$ 82

ORGANIZATION AND DESCRIPTION OF

ORGANIZATION AND DESCRIPTION OF THE BUSINESS AND FINANCIAL STATEMENT PRESENTATION	12 Months Ended
	Dec. 31, 2023
ORGANIZATION AND DESCRIPTION OF THE BUSINESS AND FINANCIAL STATEMENT PRESENTATION
ORGANIZATION AND DESCRIPTION OF THE BUSINESS AND FINANCIAL STATEMENT PRESENTATION	NOTE A – ORGANIZATION AND DESCRIPTION OF THE BUSINESS AND FINANCIAL STATEMENT PRESENTATIO N ​ Organization and Description of Business ​ ArcBest Corporation ™ ® ​ The Asset-Based segment represented approximately 63% of the Company’s 2023 total revenues before other revenues and intercompany eliminations. As of December 2023, approximately 82% of the Asset-Based segment’s employees were covered under a collective bargaining agreement, the ABF National Master Freight Agreement (the “2023 ABF NMFA”), with the International Brotherhood of Teamsters (the “IBT”), which was ratified on June 30, 2023 by a majority of ABF Freight’s IBT member employees. A majority of the 2023 ABF NMFA supplements also passed. The remaining supplements were ratified on July 7, 2023. The 2023 ABF NMFA was implemented on July 16, 2023, effective retroactive to July 1, 2023, and will remain in effect through June 30, 2028. ​ Financial Statement Presentation ​ Consolidation: ​ Segment Information: ​ Use of Estimates: ​ Reclassifications: ​ Certain reclassifications have been made to the prior period presentation of other long-term liabilities to conform to the current-year presentation of the contingent consideration liability on a separate line in the consolidated balance sheets. For the years ended December 31, 2022 and 2021, certain reclassifications have been made between operating expenses lines of the Asset-Light segment to conform to the current-year presentation of certain facility rent expenses. There was no impact on total liabilities or total operating expenses as a result of these reclassifications. ​ ​ ​

ACCOUNTING POLICIES

ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2023
ACCOUNTING POLICIES
ACCOUNTING POLICIES	NOTE B – ACCOUNTING POLICIES ​ Cash, Cash Equivalents, and Short-Term Investments: ​ Certificates of deposit are valued at cost plus accrued interest, which approximates fair value. Held-to-maturity U.S. Treasury securities are recorded at amortized cost with interest and amortization of premiums and discounts included in interest income. Quarterly, the Company evaluates held-to-maturity securities for any other-than-temporary impairments related to any intention to sell or requirement to sell before its amortized costs are recovered. If a security is considered to be other-than-temporarily impaired, the difference between amortized cost and the amount that is determined to be recoverable is recorded in operating income. ​ Concentration of Credit Risk: ​ The Company’s services are provided primarily to customers throughout the United States and, to a lesser extent, Canada, Mexico, and other international locations. On a consolidated basis, the Company had no single customer representing more than 2% of its revenues in 2023, 2022, or 2021 or more than 5% of its accounts receivable balance at December 31, 2023 and 2022. The Company performs ongoing credit evaluations of its customers and generally does not require collateral. Historically, credit losses have been within management’s expectations. ​ Receivable Allowances: ​ Property, Plant and Equipment, Including Repairs and Maintenance: ​ Computer Software for Internal Use, Including Web Site Development and Cloud Computing Costs: straight-line method generally over 2 to 7 years. Capitalized costs related to cloud computing and hosting arrangements are presented within prepaid expenses in the accompanying consolidated balance sheets. The amount of costs capitalized within any period is dependent on the nature of software development activities and projects in each period. ​ Impairment Assessment of Long-Lived Assets: . ​ Assets to be disposed of are reclassified as assets held for sale at the lower of their carrying amount or fair value less cost to sell. Assets held for sale primarily represent Asset-Based segment nonoperating properties, older revenue equipment, and other equipment. Adjustments to write down assets to fair value less the amount of costs to sell are reported in operating income. Assets held for sale are expected to be disposed of by selling the assets within the next 12 months. Gains and losses on property and equipment are reported in operating income. Assets held for sale of $1.5 million and $0.8 million were reported within other long-term assets as of December 31, 2023 and 2022, respectively. ​ Business Combinations: ​ Contingent Consideration: ​ Goodwill and Intangible Assets: ​ Indefinite-lived intangible assets are also not amortized but rather are evaluated for impairment annually or more frequently if indicators of impairment exist. Consistent with goodwill, the Company typically assesses qualitative factors but may from time to time perform a quantitative assessment to determine if it is more likely than not that the fair value of indefinite-lived intangible assets is less than its carrying value; if applicable, a quantitative analysis is performed if it is determined it is more likely than not the indefinite-lived intangible is impaired. ​ The Company amortizes finite-lived intangible assets over their respective estimated useful lives. ​ Income Taxes: ​ Management applies considerable judgment in determining the consolidated income tax provision, including valuation allowances on deferred tax assets. The valuation allowance for deferred tax assets is determined by evaluating whether it is more likely than not that the benefits of deferred tax assets will be realized through future reversal of existing taxable temporary differences, taxable income in carryback years in jurisdictions in which they are allowable, projected future taxable income, or tax-planning strategies. Uncertain tax positions, which also require significant judgment, are measured to determine the amounts to be recognized in the financial statements. The income tax provision and valuation allowances are complicated by complex and frequently changing rules administered in multiple jurisdictions, including U.S. federal, state, and foreign governments. ​ Long-Term Investments: ​ Book Overdrafts: ​ Insurance Reserves ​ Liabilities for self-insured workers’ compensation and third-party casualty claims are based on the case reserve amounts plus an estimate of loss development and incurred but not reported (“IBNR”) claims, which is developed from an independent actuarial analysis. The process of determining reserve requirements utilizes historical trends and involves an evaluation of claim frequency and severity, claims management, and other factors. Case reserves are evaluated as loss experience develops and new information becomes available. Adjustments to previously estimated aggregate reserves are reflected in financial results in the periods in which they are made. Aggregate reserves represent an estimate of the costs of claims incurred, and it is possible that the ultimate liability may differ significantly from such estimates. ​ The Company develops an estimate of self-insured cargo loss and damage claims liabilities based on historical trends and certain event-specific information. Claims liabilities are recorded in accrued expenses and are not offset by insurance receivables which are reported in other accounts receivable. ​ Loss Contingencies: ​ Long-Term Debt: ​ Interest Rate Swap Derivative Instruments ​ Leases: ​ The Company elected the short-term lease exemption for all classes of assets to include real property, revenue equipment, and service, office, and other equipment. The Company adopted the policy election as a lessee for all classes of assets to account for each lease component and its related non-lease component(s) as a single lease component. In determining the discount rate, the Company uses ArcBest Corporation’s incremental borrowing rate unless the rate implicit in the lease is readily determinable when entering into a lease as a lessee. The incremental borrowing rate is determined by the price of a fully collateralized loan with similar terms based on current market rates. ​ An assessment is made on or after the effective date of newly signed contracts as to whether the contract is, or contains, a lease at the inception of a contract. The assessment is based on: (1) whether the contract involves the use of a distinct identified asset; (2) whether the Company obtains the right to substantially all the economic benefit from the use of the asset throughout the period; and (3) whether the Company has the right to direct the use of the asset. The operating right-of-use asset is measured as the initial amount of the operating lease liability, plus any initial direct costs incurred, less any prepayments prior to commencement or lease incentives received. The operating lease liability is initially measured at the present value of the lease payments, discounted using the Company’s secured incremental borrowing rate for the same term as the underlying lease unless the interest rate implicit in the lease is readily determined, then the implicit rate will be used. Lease payments included in the measurement of the lease liability are comprised of the following: (1) the fixed noncancelable lease payments, (2) payments for optional renewal periods where it is reasonably certain the renewal period will be exercised, and (3) payments for early termination options unless it is reasonably certain the lease will not be terminated early. Variable lease payments based on an index or rate are initially measured using the index or rate in effect at lease commencement and included in the measurement of the initial lease liability. Additional payments based on the change in an index or rate are recorded as a period expense when incurred. Lease modifications result in remeasurement of the lease liability. ​ Supplemental Benefit and Postretirement Health Benefit Plans: active service period of the plan participants and amortizing unrecognized prior service credits over the remaining years of service until full eligibility of the active participants at the time of the plan amendment which created the prior service credit. A corridor approach is not used for determining the amounts of net actuarial losses to be amortized. ​ The Company has not incurred service cost under the SBP since the accrual of benefits under the plan was frozen on December 31, 2009, however, the Company incurs service cost under the postretirement health benefit plan which is reported within operating expenses in the consolidated statements of operations. The other components of net periodic benefit cost (credit) of the SBP (including pension settlement expense) and the postretirement health benefit plan are reported within the other line item of other income (costs). ​ The expense and liability related to the postretirement health benefit plan are measured based upon a number of assumptions and using the services of a third-party actuary. Assumptions are made regarding the discount rate, expected retirement age, mortality, employee turnover, and future increases in health care costs. The discount rates used to discount the SBP and postretirement health benefit plan obligations are determined by matching projected cash distributions with appropriate high-quality corporate bond yields in a yield curve analysis. The assumptions used directly impact the net periodic benefit cost (credit) for a particular year. An actuarial gain or loss results when actual experience varies from the assumptions or when there are changes in actuarial assumptions. Actuarial gains and losses are not included in net periodic benefit cost (credit) in the period when they arise but are recognized as a component of other comprehensive income or loss and subsequently amortized as a component of net periodic benefit cost (credit). ​ The Company uses December 31 as the measurement date for the SBP and postretirement health benefit plan. Plan obligations are also remeasured upon curtailment and upon settlement. Benefit distributions under the SBP individually exceed the annual interest cost of the plan, which triggers settlement accounting. The Company records the related settlement expense when the amount of the benefit to be distributed is fixed, which is generally upon an employee’s termination of employment. There was no pension settlement expense incurred for the SBP in 2023, 2022, or 2021. ​ Revenue Recognition: ​ Asset-Based Segment Asset-Based segment revenues consist primarily of less-than-truckload freight delivery. Performance obligations are satisfied upon final delivery of the freight to the specified destination. Revenue is recognized based on the relative transit time in each reporting period with expenses recognized as incurred. A bill-by-bill analysis is used to establish estimates of revenue in transit for recognition in the appropriate period. Because the bill-by-bill methodology utilizes the approximate location of the shipment in the delivery process to determine the revenue to recognize, management believes it to be a reliable method. ​ Certain contracts may provide for volume-based or other discounts which are accounted for as variable consideration. The Company estimates these amounts based on a historical expectation of discounts to be earned by customers, and revenue is recognized based on the estimates. Management believes that actual amounts will not vary significantly from estimates of variable consideration. ​ Revenue, purchased transportation expense, and third-party service expenses are reported on a gross basis for certain shipments and services where the Company utilizes a third-party carrier for pickup, linehaul, delivery of freight, or performance of services but remains primarily responsible for fulfilling delivery to the customer and maintains discretion in setting the price for the services. ​ Asset-Light Segment Asset-Light segment revenues consist primarily of asset-light logistics services using third-party vendors to provide transportation services. Asset-Light segment revenue is generally recognized based on the relative transit time in each reporting period using estimated standard delivery times for freight in transit at the end of the reporting period. Purchased transportation expense is recognized as incurred consistent with the recognition of revenue. ​ Revenue and purchased transportation expense are reported on a gross basis for shipments and services where the Company utilizes a third-party carrier for pickup and delivery but remains primarily responsible to the customer for delivery and maintains discretion in setting the price for the service. ​ Other Recognition and Disclosure Payment terms with customers may vary depending on the service provided, location or specific agreement with the customer. The term between invoicing and when payment is due is not significant. For certain services, payment is required before the services are provided to the customer. ​ The Company expenses sales commissions when incurred because the amortization period is one year or less. ​ The Company has elected not to disclose the value of unsatisfied performance obligations for contracts with an original length of one year or less or contracts for which revenue is recognized at the amount to which the Company has the right to invoice for services performed. ​ Comprehensive Income or Loss: ​ Accelerated Share Repurchase: ​ Earnings Per Share: ​ Share-Based Compensation: ​ Share-based awards are amortized to compensation expense on a straight-line basis over the vesting period of awards or over the period to which the recipient first becomes eligible for retirement, whichever is shorter, with vesting accelerated upon death or disability. The Company recognizes forfeitures as they occur, and the income tax effects of awards are recognized in the statement of operations when awards vest or are settled. ​ Fair Value Measurements: ​ ● Level 1 – Quoted prices for identical assets and liabilities in active markets. ● Level 2 – Quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. ● Level 3 – Unobservable inputs (Company’s market assumptions) that are significant to the valuation model. ​ Environmental Matters: ​ Exit or Disposal Activities: ​ Accounting Pronouncements Not Yet Adopted ​ Accounting Standards Codification (“ASC”) Topic 280, Segment Reporting Improvements to Reportable Segment Disclosures ​ ASC Topic 740 , Income Taxes, Improvements to Income Tax Disclosures ​

FINANCIAL INSTRUMENTS AND FAIR

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2023
FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS
FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS	NOTE C – FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS ​ Financial Instruments ​ The following table presents the components of cash and cash equivalents and short-term investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 December 31 ​ ​ 2023 ​ 2022 ​ ​ (in thousands) ​ Cash and cash equivalents ​ ​ ​ ​ ​ ​ ​ Cash deposits (1) ​ $ 168,472 ​ $ 137,247 ​ Variable rate demand notes (1)(2) ​ — ​ 9,285 ​ Money market funds (3) ​ 93,754 ​ 11,732 ​ Total cash and cash equivalents ​ $ 262,226 ​ $ 158,264 ​ ​ ​ ​ ​ ​ ​ ​ ​ Short-term investments ​ ​ ​ ​ ​ ​ ​ Certificates of deposit (1) ​ $ 67,842 ​ $ 88,851 ​ U.S. Treasury securities (4) ​ ​ — ​ ​ 78,811 ​ Total short-term investments ​ $ 67,842 ​ $ 167,662 ​ (1) Recorded at cost plus accrued interest, which approximates fair value. (2) Amounts may be redeemed on a daily basis with the original issuer. (3) Recorded at fair value as determined by quoted market prices (see amounts presented in the table of financial assets and liabilities measured at fair value within this Note). (4) Recorded at amortized cost plus accrued interest, which approximates fair value. U.S. Treasury securities included in short-term investments are held-to-maturity investments with maturity dates of less than one year. ​ The Company’s long-term financial instruments are presented in the table of financial assets and liabilities measured at fair value within this Note. ​ Concentrations of Credit Risk of Financial Instruments The Company is potentially subject to concentrations of credit risk related to its cash, cash equivalents, and short-term investments. The Company reduces credit risk by maintaining its cash deposits and short-term investments in accounts and certificates of deposit which are primarily FDIC-insured or in direct obligations of the U.S. government. However, certain cash deposits and certificates of deposit may exceed federally insured limits. At December 31, 2023 and 2022, cash deposits and short-term investments totaling $76.3 million and $87.6 million, respectively, were neither FDIC insured nor direct obligations of the U.S. government. The Company also holds money market funds, which are invested in U.S. government securities and repurchase agreements collateralized solely by U.S. government securities. ​ ​ Fair value and carrying value disclosures of financial instruments as of December 31 are presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 ​ ​ (in thousands) ​ ​ ​ ​ Carrying ​ Fair ​ Carrying ​ Fair ​ ​ ​ ​ Value ​ Value ​ Value ​ Value ​ Credit Facility (1) ​ $ 50,000 ​ $ 50,000 ​ $ 50,000 ​ $ 50,000 ​ Notes payable (2) ​ 178,938 ​ 177,149 ​ 214,623 ​ 207,778 ​ New England Pension Fund withdrawal liability (3) ​ ​ 19,402 ​ ​ 18,220 ​ ​ 20,100 ​ ​ 18,911 ​ ​ ​ $ 248,340 ​ $ 245,369 ​ $ 284,723 ​ $ 276,689 ​ (1) The revolving credit facility (the “Credit Facility”) carries a variable interest rate based on Secured Overnight Financing Rate (“SOFR”), plus a margin, priced at market for debt instruments having similar terms and collateral requirements (Level 2 of the fair value hierarchy). (2) Fair value of the notes payable was determined using a present value income approach based on quoted interest rates from lending institutions with which the Company would enter into similar transactions (Level 2 of the fair value hierarchy). (3) ABF Freight’s multiemployer pension plan obligation with the New England Teamsters and Trucking Industry Pension Fund (the “New England Pension Fund”) was restructured under a transition agreement effective on August 1, 2018, which resulted in a related withdrawal liability. The fair value of the outstanding withdrawal liability is equal to the present value of the future withdrawal liability payments, discounted at an interest rate of 5.3% at both December 31, 2023 and 2022, determined using the 20-year U.S. Treasury rate plus a spread (Level 2 of the fair value hierarchy). As of December 31, 2023, the outstanding withdrawal liability totaled $19.4 million, of which $0.7 million was recorded in accrued expenses and the remaining portion was recorded in other long-term liabilities. ​ ​ Assets and Liabilities Measured at Fair Value on a Recurring Basis ​ The following table presents the assets and liabilities that are measured at fair value on a recurring basis: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ ​ ​ ​ ​ Quoted Prices Significant Significant ​ ​ ​ ​ ​ In Active ​ Observable ​ Unobservable ​ ​ ​ ​ ​ ​ Markets ​ Inputs ​ Inputs ​ ​ ​ Total (Level 1) (Level 2) (Level 3) ​ ​ (in thousands) ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (1) ​ $ 93,754 ​ $ 93,754 ​ $ — ​ $ — ​ Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan (2) ​ 4,627 ​ 4,627 ​ — ​ — ​ Interest rate swap (3) ​ ​ 1,710 ​ ​ — ​ ​ 1,710 ​ ​ — ​ ​ ​ $ 100,091 ​ $ 98,381 ​ $ 1,710 ​ $ — ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration (4) ​ ​ 92,900 ​ ​ — ​ ​ — ​ ​ 92,900 ​ ​ ​ $ 92,900 ​ $ — ​ $ — ​ $ 92,900 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ ​ ​ ​ ​ Quoted Prices Significant Significant ​ ​ ​ ​ ​ In Active ​ Observable ​ Unobservable ​ ​ ​ ​ ​ ​ Markets ​ Inputs ​ Inputs ​ ​ ​ Total (Level 1) (Level 2) (Level 3) ​ ​ (in thousands) ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (1) ​ $ 11,732 ​ $ 11,732 ​ $ — ​ $ — ​ Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan (2) ​ 3,982 ​ 3,982 ​ — ​ — ​ Interest rate swap (3) ​ ​ 3,526 ​ ​ — ​ ​ 3,526 ​ ​ — ​ ​ ​ $ 19,240 ​ $ 15,714 ​ $ 3,526 ​ $ — ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration (4) ​ ​ 112,000 ​ ​ — ​ ​ — ​ ​ 112,000 ​ ​ ​ $ 112,000 ​ $ — ​ $ — ​ $ 112,000 ​ ​ ​ (1) Included in cash and cash equivalents. (2) Nonqualified deferred compensation plan investments consist of U.S. and international equity mutual funds, government and corporate bond mutual funds, and money market funds which are held in a trust with a third-party brokerage firm. Included in other long-term assets, with a corresponding liability reported within other long-term liabilities. (3) Included in other long-term assets. The fair value of the interest rate swap was determined by discounting future cash flows and receipts based on expected interest rates observed in market interest rate curves adjusted for estimated credit valuation considerations reflecting nonperformance risk of the Company and the counterparty, which are generally considered to be in Level 3 of the fair value hierarchy. However, the Company assessed Level 3 inputs as insignificant to the valuation at December 31, 2023 and 2022 and considers the interest rate swap valuation in Level 2 of the fair value hierarchy. (4) Included as a long-term liability, based on the December 31, 2023 remeasurement as the 2023 target was not achieved. As part of the Agreement and Plan of Merger (the “Merger Agreement”) of MoLo, executed on November 1, 2021, certain additional cash consideration is required to be paid by the Company based on the achievement of certain incremental targets of adjusted EBITDA for each of the years ended December 31, 2023, 2024, and 2025 (see Note E). The estimated fair value of contingent consideration is determined by assessing Level 3 inputs. The Level 3 assessments utilize a Monte Carlo simulation with inputs including scenarios of estimated revenues and adjusted EBITDA to be achieved for the applicable performance periods, volatility factors applied to the simulations, and the discount rate applied, which was 13.3% and 14.0% as of December 2023 and 2022, respectively. Changes in the significant unobservable inputs might result in a significantly higher or lower fair value at the reporting date. The decrease in fair value of contingent earnout consideration as of December 31, 2023, compared to December 31, 2022, reflects revised assumptions for business growth in 2024 and 2025, as well as the impact of softer market conditions during 2023, despite a lower discount rate at the December 31, 2023 remeasurement date. ​ The following table provides the changes in fair value of the liabilities measured at fair value using inputs categorized in Level 3 of the fair value hierarchy: ​ ​ ​ ​ ​ ​ ​ ​ Contingent Consideration ​ ​ ​ (in thousands) ​ Balance at December 31, 2022 ​ $ 112,000 ​ Change in fair value included in operating income ​ ​ (19,100) ​ Balance at December 31, 2023 ​ $ 92,900 ​ ​ Assets Measured at Fair Value on a Nonrecurring Basis ​ The Company remeasures certain assets on a nonrecurring basis upon the occurrence of certain events. During the year ended December 31, 2023, the Company remeasured the fair value of its equity investments in private entities upon an observable price change and remeasured certain long-lived operating lease right-of-use assets and leasehold improvements for which impairment charges were recognized during the period. ​ The following table provides the change in fair value of equity investments on a nonrecurring basis using inputs categorized in Level 3 of the fair value hierarchy: ​ ​ ​ ​ ​ ​ ​ ​ Equity Investment (1) ​ ​ (in thousands) ​ Balance at December 31, 2022 ​ $ 25,000 ​ Change in fair value included in operating income ​ ​ 3,739 ​ Balance at December 31, 2023 ​ $ 28,739 ​ (1) Represents the Company’s equity investment in Phantom Auto, a provider of human-centered remote operation software. The equity investment is accounted for as a nonmarketable equity security without a readily determinable value using the measurement alternative, which allows for the investment to be recorded at cost, less any impairment and adjusted for observable price changes in orderly transactions for an identical or similar equity security of the same issuer. The $3.7 million increase in fair value of the Company’s equity investment was measured as of April 26, 2023, based on an observable price change upon the closing of Phantom Auto’s Series B-2 funding round. The fair value of the investment was estimated using a hybrid method of the Black-Scholes option pricing model and the probability-weighted expected return method. This method produces a per-share value based on a probability-weighted scenario analysis. The scenarios reflect changes to the liquidation preferences based on the potential liquidity event. The Black-Scholes option pricing model used various inputs, including expected volatility, expected term to liquidity, risk-free rate over the expected term, breakpoints values, and liquidation preferences. ​ The following table provides the changes in the long-lived assets measured on a nonrecurring basis for which impairment charges were recognized during the year ended December 31, 2023. The fair value measurements used inputs categorized in Level 3 of the fair value hierarchy. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Lease ​ ​ ​ ​ ​ Carrying Value Impairment Charges (1) Fair Value ​ ​ (in thousands) ​ Operating right-of-use assets ​ $ 48,417 ​ $ (28,124) ​ $ 20,293 ​ Leasehold improvements ​ ​ 3,874 ​ ​ (2,038) ​ ​ 1,836 ​ ​ ​ $ 52,291 ​ $ (30,162) ​ $ 22,129 ​ (1) During the third quarter of 2023, the Company recorded impairment charges of $30.2 million related to operating right-of-use assets and leasehold improvements associated with a freight handling pilot facility, a service center, and office spaces that were made available for sublease. The fair value of these asset groups was estimated at September 1, 2023, using a discounted cash flow method utilizing market-participant discount rates ranging from 7.5% to 9.5% and certain unobservable inputs, including estimated cash flows based on anticipated future sublease terms as determined using third-party real estate broker quotes. See Note H for additional discussion related to these impairment charges. ​ There were no assets remeasured on a nonrecurring basis during the year ended December 31, 2022.

DISCONTINUED OPERATIONS

DISCONTINUED OPERATIONS	12 Months Ended
	Dec. 31, 2023
DISCONTINUED OPERATIONS
DISCONTINUED OPERATIONS	NOTE D – DISCONTINUED OPERATIONS ​ On February 28, 2023, the Company sold FleetNet, a wholly owned subsidiary of the Company, for an aggregate adjusted cash purchase price of $100.9 million, and recorded a pre-tax gain on sale of $70.2 million, or $52.3 million, net of tax. FleetNet provided roadside repair solutions and vehicle maintenance management services for commercial and private fleets through a network of third-party service providers. The sale of FleetNet allows the Company to focus on growing its continuing operations, as FleetNet was no longer core to the Company’s growth initiatives. The financial results of FleetNet have been accounted for as discontinued operations for all periods presented. ​ The following table summarizes the financial results from discontinued operations: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31 ​ ​ 2023 ​ 2022 ​ 2021 ​ ​ (in thousands) Revenues ​ $ 55,929 ​ $ 295,043 ​ $ 213,882 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain on sale of business (1) ​ ​ (70,201) ​ ​ — ​ ​ — Other ​ ​ 54,623 ​ ​ 290,300 ​ ​ 209,874 ​ ​ ​ (15,578) ​ ​ 290,300 ​ ​ 209,874 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating income ​ ​ 71,507 ​ ​ 4,743 ​ ​ 4,008 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other income, net (2) ​ ​ 17 ​ ​ 109 ​ ​ 59 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income from discontinued operations before income taxes ​ ​ 71,524 ​ ​ 4,852 ​ ​ 4,067 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax provision ​ ​ 18,255 ​ ​ 1,291 ​ ​ 1,005 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income from discontinued operations, net of tax ​ $ 53,269 ​ $ 3,561 ​ $ 3,062 (1) The gain recognized during the year ended December 31, 2023 includes post-closing adjustments, including the resolution of certain post-close contingencies in the second quarter of 2023. The total pre-tax gain of $70.2 million includes transaction costs of $3.8 million consisting of consulting fees, professional fees, and employee-related expenses. (2) Includes interest income, net of interest expense, of which the amounts are immaterial for all periods presented. ​ The following table summarizes the assets and liabilities from discontinued operations: ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ ​ (in thousands) ​ Cash and cash equivalents ​ $ 108 ​ Accounts receivable, net ​ ​ 63,022 ​ Other current assets ​ ​ 1,606 ​ Total current assets of discontinued operations ​ $ 64,736 ​ ​ ​ ​ ​ ​ Property, plant and equipment, net ​ ​ 10,350 ​ Goodwill ​ ​ 630 ​ Intangible assets, net ​ ​ 63 ​ Other long-term assets ​ ​ 54 ​ Total long-term assets of discontinued operations ​ $ 11,097 ​ ​ ​ ​ ​ ​ Accounts payable ​ ​ 47,687 ​ Income taxes payable ​ ​ 613 ​ Accrued expenses ​ ​ 3,365 ​ Total current liabilities of discontinued operations ​ $ 51,665 ​ ​ ​ ​ ​ ​ Deferred tax liability ​ ​ 781 ​ Total long-term liabilities of discontinued operations ​ $ 781 ​ ​ Cash flows from discontinued operations of FleetNet were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31 ​ 2023 2022 ​ ​ (in thousands) Net cash provided by operating activities (1) ​ $ 762 ​ $ 2,825 ​ Net cash used in investing activities (2) ​ ​ (397) ​ ​ (3,329) ​ Net cash provided by (used in) financing activities ​ ​ (473) ​ ​ 560 ​ Net increase (decrease) in cash and cash equivalents ​ $ (108) ​ $ 56 ​ (1) Includes depreciation and amortization expense of $0.4 million and $1.9 million for the years ended December 31, 2023 and 2022, respectively. Also includes share-based compensation expense for the year ended December 31, 2023 of $0.3 million, which is included in the “Pre-tax gain on sale of discontinued operations” line of the consolidated statements of cash flows. (2) Includes purchases of property, plant and equipment of $0.1 million and $1.4 million for the years ended December 31, 2023 and 2022, respectively. Excludes the proceeds from the sale of discontinued operations, which are included in cash flows from continuing operations. ​

ACQUISITION

ACQUISITION	12 Months Ended
	Dec. 31, 2023
ACQUISITION.
ACQUISITION	NOTE E – ACQUISITION ​ On November 1, 2021 (the “acquisition date”), the Company acquired MoLo, a Chicago-based truckload freight brokerage company, pursuant to the Merger Agreement dated September 29, 2021. Net cash consideration related to the transaction totaled $237.1 million, adjusted for certain post-closing adjustments. The Company funded the initial purchase price with cash on hand and subsequently received $2.3 million from escrow related to certain post-closing adjustments during the year ended December 31, 2022, which is reported in the accompanying consolidated statements of cash flows as business acquisition, net of cash acquired. The Merger Agreement provides for certain additional cash consideration to be paid by the Company based on the achievement of certain incremental targets of adjusted EBITDA for each of the years ended December 31, 2023, 2024, and 2025. The adjusted EBITDA metric was below target for 2023, resulting in no earnout payment for 2023. At 100% of the target, the cumulative additional consideration through 2025 would be $215.0 million, consisting of target earnout payments of $70.0 million and $145.0 million, including catch-up provisions, for the years ended December 31, 2024 and 2025, respectively. Possible undiscounted cash consideration could range from a total of $95.0 million at 80% of target to $455.0 million at 300% of target, as outlined in the Merger Agreement. See Note C for change in fair value of the contingent earnout consideration. ​ The results of MoLo’s operations subsequent to the acquisition date have been included in the accompanying consolidated financial statements, with the acquired operations included within the Asset-Light operating segment (see Note O). The acquisition of MoLo enhances the scale of the Company’s truckload brokerage services by providing additional truckload capacity, support, and expertise in the Company’s Asset-Light operations and increasing cross-selling potential. ​ In the year of acquisition, operating revenues of $120.3 million and operating loss of $1.2 million, including intangible asset amortization expense, related to MoLo from the acquisition date through December 31, 2021 were included in the accompanying consolidated statements of operations. The Company recognized $6.0 million of acquisition related costs in operating expenses in 2021. For segment reporting purposes, these transaction costs have been reported in “Other and eliminations” (see Note O).

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2023
GOODWILL AND INTANGIBLE ASSETS
GOODWILL AND INTANGIBLE ASSETS	NOTE F – GOODWILL AND INTANGIBLE ASSETS ​ December 31, 2022 and 2021 goodwill balances have been adjusted to reclassify $0.6 million of goodwill related to FleetNet to discontinued operations. The remaining goodwill balance of $304.8 million at both December 31, 2023 and 2022, primarily relates to the Asset-Light segment acquisitions of MoLo and Panther. ​ Goodwill balances were as follows: ​ ​ ​ ​ ​ ​ ​ Goodwill ​ ​ (in thousands) ​ Balances at December 31, 2021 ​ $ 299,708 ​ Purchase accounting adjustments (1) ​ 5,045 ​ Balances at December 31, 2023 and 2022 ​ $ 304,753 ​ ​ ​ ​ ​ ​ Accumulated impairment at December 31, 2023 and 2022 ​ $ (20,000) ​ (1) Measurement period purchase accounting adjustments represent adjustments to the acquired balance of working capital and goodwill related to the November 1, 2021 acquisition of MoLo. ​ The annual impairment evaluation of the goodwill balance of the Asset-Light reporting unit was performed as of October 1, 2023, and it was determined that there was no impairment to the recorded balance. In making this analysis, management considered current and forecasted business levels and estimated future cash flows over several years. Furthermore, as of December 31, 2023, no indicators of impairment were identified. Goodwill was assessed for impairment qualitatively as of October 1, 2022, and the evaluation determined there was no impairment of the goodwill balance. ​ Intangible assets consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ December 31, 2022 ​ ​ Weighted-Average ​ ​ ​ ​ Accumulated ​ Net ​ ​ ​ ​ Accumulated ​ Net ​ Amortization Period Cost Amortization Value ​ Cost Amortization Value ​ ​ (in years) ​ (in thousands) ​ (in thousands) Finite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Customer relationships 12 ​ $ 99,579 ​ $ 51,357 ​ $ 48,222 ​ $ 99,579 ​ $ 42,933 ​ $ 56,646 ​ Other ​ 8 ​ ​ 30,151 ​ ​ 9,523 ​ ​ 20,628 ​ ​ 29,914 ​ ​ 5,127 ​ ​ 24,787 ​ ​ 11 ​ 129,730 ​ 60,880 ​ 68,850 ​ ​ 129,493 ​ 48,060 ​ 81,433 ​ Indefinite-lived intangible asset ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trade name N/A ​ 32,300 ​ N/A ​ 32,300 ​ ​ 32,300 ​ N/A ​ 32,300 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total intangible assets N/A ​ $ 162,030 ​ $ 60,880 ​ $ 101,150 ​ $ 161,793 ​ $ 48,060 ​ $ 113,733 ​ ​ ​ The annual impairment evaluation of the indefinite-lived intangible asset was performed as of October 1, 2023 and 2022, and it was determined that there was no impairment of the recorded balance. ​ As of December 31, 2023, the future amortization for intangible assets acquired through business acquisitions were as follows: ​ ​ ​ ​ ​ ​ ​ Amortization of ​ ​ Intangible Assets ​ ​ (in thousands) ​ 2024 ​ $ 12,790 ​ 2025 ​ 12,790 ​ 2026 ​ 8,683 ​ 2027 ​ 7,258 ​ 2028 ​ ​ 7,259 ​ Thereafter ​ ​ 20,070 ​ Total amortization ​ $ 68,850 ​ ​

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2023
INCOME TAXES
INCOME TAXES	NOTE G – INCOME TAXES ​ Significant components of the provision or benefit for income taxes for the years ended December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands) Current provision on continuing operations: ​ ​ ​ ​ Federal ​ $ 38,860 ​ $ 79,477 ​ $ 55,684 ​ State ​ 10,949 ​ 19,713 ​ 14,229 ​ Foreign ​ 508 ​ 869 ​ 341 ​ ​ ​ 50,317 ​ 100,059 ​ 70,254 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred benefit on continuing operations: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ (4,882) ​ (5,591) ​ (6,119) ​ State ​ (682) ​ (793) ​ (1,570) ​ Foreign ​ (2) ​ (20) ​ 63 ​ ​ ​ (5,566) ​ (6,404) ​ (7,626) ​ Total provision for income taxes on continuing operations ​ $ 44,751 ​ $ 93,655 ​ $ 62,628 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current provision on discontinued operations: ​ ​ ​ ​ Federal ​ $ 14,656 ​ $ 901 ​ $ 767 ​ State ​ 3,599 ​ 236 ​ 201 ​ ​ ​ 18,255 ​ 1,137 ​ 968 ​ Deferred provision on discontinued operations: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ — ​ 114 ​ 21 ​ State ​ — ​ 40 ​ 16 ​ ​ ​ — ​ 154 ​ 37 ​ Total provision for income taxes on discontinued operations ​ $ 18,255 ​ $ 1,291 ​ $ 1,005 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total provision for income taxes ​ $ 63,006 ​ $ 94,946 ​ $ 63,633 ​ ​ Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Components of the deferred tax benefit on continuing operations for the years ended December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 ​ 2022 ​ 2021 ​ ​ (in thousands) Amortization, depreciation, and basis differences for property, plant and equipment and other long-lived assets (1) $ 1,744 $ 4,274 $ 1,409 ​ Amortization of intangibles ​ 6,127 ​ (2,995) ​ (555) ​ Changes in reserves for workers’ compensation, third-party casualty, and cargo claims ​ (4,975) ​ (3,713) ​ (3,296) ​ Revenue recognition ​ (50) ​ 6 ​ (1,434) ​ Allowance for credit losses ​ 1,094 ​ (388) ​ 170 ​ Nonunion pension and other retirement plans ​ (3) ​ (4) ​ (3) ​ Multiemployer pension fund withdrawal ​ ​ 180 ​ ​ 172 ​ ​ 164 ​ Federal and state net operating loss carryforwards utilized (generated) ​ (758) ​ 899 ​ (300) ​ State depreciation adjustments ​ (456) ​ (915) ​ 598 ​ Share-based compensation ​ 531 ​ 737 ​ (949) ​ Valuation allowance increase (decrease) ​ 44 ​ (489) ​ 912 ​ Other accrued expenses ​ (2,143) ​ (3,069) ​ (4,056) ​ Prepaid expenses ​ ​ 313 ​ ​ (18) ​ ​ (788) ​ Operating lease right-of-use assets/liabilities – net ​ ​ (8,065) ​ ​ (651) ​ ​ (228) ​ Other ​ 851 ​ (250) ​ 730 ​ Deferred tax benefit ​ $ (5,566) ​ $ (6,404) ​ $ (7,626) ​ (1) The Tax Cuts and Jobs Act , enacted in December 2017, allowed first year bonus depreciation at 100% for assets placed into service between September 27, 2017 and January 1, 2023. Due to an increase in the purchase of assets eligible for 100% depreciation, the deferred tax expense related to the tax depreciation expense in excess of book depreciation increased in 2022, compared to 2021. ​ ​ Significant components of the deferred tax assets and liabilities of continuing operations at December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 ​ 2022 ​ ​ (in thousands) Deferred tax assets: ​ ​ ​ Accrued expenses ​ $ 60,842 ​ $ 53,785 ​ Operating lease right-of-use liabilities ​ ​ 53,589 ​ ​ 46,056 ​ Supplemental pension liabilities ​ ​ 85 ​ ​ 81 ​ Multiemployer pension fund withdrawal ​ ​ 4,871 ​ ​ 5,063 ​ Postretirement liabilities other than pensions ​ 3,389 ​ 3,137 ​ Share-based compensation ​ 5,249 ​ 5,622 ​ Federal and state net operating loss carryovers ​ 1,511 ​ 753 ​ Receivable allowances ​ ​ 1,951 ​ ​ 2,967 ​ Other ​ 709 ​ 417 ​ Total deferred tax assets ​ 132,196 ​ 117,881 ​ Valuation allowance ​ (1,751) ​ (1,707) ​ Total deferred tax assets, net of valuation allowance ​ 130,445 ​ 116,174 ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ ​ Amortization, depreciation, and basis differences for property, plant and equipment, and other long-lived assets ​ 118,211 ​ 116,290 ​ Operating lease right-of-use assets ​ ​ 43,938 ​ ​ 44,170 ​ Intangibles ​ 10,256 ​ 4,442 ​ Prepaid expenses ​ 5,685 ​ 5,424 ​ Total deferred tax liabilities ​ 178,090 ​ 170,326 ​ Net deferred tax liabilities ​ $ (47,645) ​ $ (54,152) ​ ​ Reconciliation between the effective income tax rate, as computed on income from continuing operations before income taxes, and the statutory federal income tax rate for the years ended December 31 is presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 ​ 2022 ​ 2021 ​ ​ (in thousands, except percentages) Income tax provision at the statutory federal rate of 21.0% $ 39,252 $ 81,544 $ 57,348 ​ Federal income tax effects of: ​ ​ ​ ​ ​ ​ ​ ​ ​ State income taxes ​ (2,156) ​ (3,973) ​ (2,658) ​ Nondeductible expenses ​ 4,040 ​ 5,606 ​ 3,596 ​ Life insurance proceeds and changes in cash surrender value ​ (962) ​ 575 ​ (866) ​ Alternative fuel credit ​ (1,302) ​ (2,449) ​ — ​ Net increase (decrease) in valuation allowances ​ 44 ​ (464) ​ 887 ​ Net increase in uncertain tax positions ​ ​ — ​ ​ — ​ ​ 854 ​ Settlement of share-based compensation ​ ​ (3,989) ​ ​ (6,693) ​ ​ (6,021) ​ Foreign tax credits generated ​ ​ (506) ​ ​ (849) ​ ​ (404) ​ Federal research and development tax credits ​ ​ (75) ​ ​ 278 ​ ​ (2,044) ​ Other ​ (368) ​ 311 ​ (1,127) ​ Federal income tax provision ​ 33,978 ​ 73,886 ​ 49,565 ​ State income tax provision ​ 10,267 ​ 18,920 ​ 12,659 ​ Foreign income tax provision ​ 506 ​ 849 ​ 404 ​ Total provision for income taxes ​ $ 44,751 ​ $ 93,655 ​ $ 62,628 ​ Effective tax rate ​ 23.9 % 24.1 % 22.9 % ​ The Company's total effective tax rate was 24.4%, 24.1% and 23.0% for 2023, 2022 and 2021, respectively, including discontinued operations which are further discussed in Note D. The effective tax rate from discontinued operations was 25.5%, 26.6% and 24.7% for 2023, 2022 and 2021, respectively. State tax rates vary among states and average approximately 6.0% to 6.5%, although some state rates are higher, and a small number of states do not impose an income tax. ​ Income taxes paid, excluding income tax refunds, totaled $115.7 million, $148.7 million, and $77.5 million in 2023, 2022, and 2021, respectively. Income tax refunds totaled $36.4 million, $42.3 million, and $19.4 million in 2023, 2022, and 2021, respectively. ​ Under Accounting Standards Codification Topic 718, Compensation – Stock Compensation ​ At December 31, 2023, the Company had gross federal net operating loss carryforwards of $0.6 million. Due to taxable income, there is no need for a valuation allowance on these amounts at December 31, 2023 or 2022. At December 31, 2023, the Company had total gross state net operating losses of $26.4 million. Gross state net operating losses of $1.4 million are from the acquisition of Panther and relate to periods ending on or prior to June 15, 2012. State carryforward periods for the remaining Panther net operating losses vary from 10 ​ As the Canadian tax rate is now higher than the U.S. tax rate, it is unlikely that foreign tax credit carryforwards will be useable, as U.S. taxes will be paid at a lower rate than the tax rates in Canada. Thus, the foreign tax credit carryover is fully reserved, resulting in valuation allowances of $1.0 million at December 31, 2023 and 2022. ​ Consolidated federal income tax returns filed for tax years through 2019 are closed by the applicable statute of limitations. The Company is not under examination by any federal, state, or foreign taxing authorities at December 31, 2023. ​ At December 31, 2023 and 2022, there was a reserve for uncertain tax positions of $0.9 million related to credits taken on federal returns, of which $0.5 million will reverse in the second quarter of 2024 upon the expiration of the statute of limitations. ​ For 2023, 2022, and 2021, interest paid or accrued related to foreign and state income taxes was immaterial.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2023
LEASES
LEASES	​ NOTE H – LEASES ​ The Company has operating lease arrangements for certain facilities and revenue equipment used in the Asset-Based and Asset-Light segment operations and certain other facilities and office equipment. Current operating leases have remaining terms of 9.8 years or less, some of which include one or more options to renew, with renewal option terms up to ten years. There is one early termination option available on an operating lease as of December 31, 2023, provided notification is given 24 months prior to the end of the lease term, which is included in the right-of-use assets and liabilities as of December 31, 2023. All renewal options that have been exercised or are reasonably certain to be exercised as of December 31, 2023 and 2022, are included in the right-of-use assets and lease liabilities. Variable lease cost for operating leases consists of subsequent changes in the consumer price index, rent payments that are based on usage, and other lease related payments which are subject to change and not considered fixed payments. All fixed lease and non-lease component payments are combined in determining the right-of-use asset and lease liability. ​ The components of operating lease expense were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31 ​ 2023 2022 2021 ​ ​ (in thousands) Operating lease expense ​ $ 38,794 ​ $ 31,790 ​ $ 26,552 Variable lease expense ​ ​ 6,804 ​ ​ 4,188 ​ ​ 4,128 Sublease income ​ ​ (246) ​ ​ (391) ​ ​ (626) Total operating lease expense (1) ​ $ 45,352 ​ $ 35,587 ​ $ 30,054 (1) Operating lease expense excludes short-term leases with a term of 12 months or less. ​ The operating cash flows from operating lease activity were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31 ​ ​ 2023 2022 2021 ​ ​ (in thousands) ​ Noncash change in operating right-of-use assets ​ $ 33,470 ​ $ 27,465 ​ $ 24,023 ​ Change in operating lease liabilities ​ ​ (30,550) ​ ​ (24,513) ​ ​ (23,400) ​ Operating right-of-use-assets and lease liabilities, net ​ $ 2,920 ​ $ 2,952 ​ $ 623 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid for amounts included in the measurement of operating lease liabilities ​ $ (35,759) ​ $ (28,830) ​ $ (25,909) ​ ​ Supplemental balance sheet information related to operating leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ ​ (in thousands, except lease term and discount rate) ​ ​ ​ ​ ​ Land and ​ Equipment ​ ​ ​ Total ​ Structures ​ and Others Operating right-of-use assets (long-term) ​ $ 169,999 ​ $ 169,663 ​ $ 336 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease liabilities (current) ​ $ 32,172 ​ $ 31,865 ​ $ 307 Operating lease liabilities (long-term) ​ 176,621 ​ ​ 176,598 ​ ​ 23 Total operating lease liabilities ​ $ 208,793 ​ $ 208,463 ​ $ 330 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term (in years) ​ ​ 7.4 ​ ​ ​ ​ ​ ​ Weighted-average discount rate ​ ​ 4.29% ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ (in thousands, except lease term and discount rate) ​ ​ ​ ​ ​ ​ Land and ​ Equipment ​ ​ ​ ​ Total ​ Structures ​ and Others ​ Operating right-of-use assets (long-term) ​ $ 166,515 ​ $ 165,822 ​ $ 693 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease liabilities (current) ​ $ 26,225 ​ $ 25,824 ​ $ 401 ​ Operating lease liabilities (long-term) ​ 147,828 ​ ​ 147,534 ​ ​ 294 ​ Total operating lease liabilities ​ $ 174,053 ​ $ 173,358 ​ $ 695 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term (in years) ​ ​ 7.6 ​ ​ ​ ​ ​ ​ ​ Weighted-average discount rate ​ ​ 3.58% ​ ​ ​ ​ ​ ​ ​ ​ Maturities of operating lease liabilities at December 31, 2023 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equipment ​ ​ ​ ​ ​ ​ Land and ​ and ​ ​ Total Structures (1) Other ​ (in thousands) ​ 2024 ​ $ 40,218 ​ $ 39,905 ​ $ 313 ​ 2025 ​ 36,458 ​ 36,435 ​ 23 ​ 2026 ​ 33,187 ​ 33,187 ​ — ​ 2027 ​ 27,071 ​ 27,071 ​ — ​ 2028 ​ 24,033 ​ 24,033 ​ — ​ Thereafter ​ 86,011 ​ 86,011 ​ — ​ Total lease payments ​ ​ 246,978 ​ ​ 246,642 ​ ​ 336 ​ Less imputed interest ​ ​ (38,185) ​ ​ (38,179) ​ ​ (6) ​ Total ​ $ 208,793 ​ $ 208,463 ​ $ 330 ​ ​ (1) Excludes future minimum lease payments for leases which were executed but had not yet commenced as of December 31, 2023, of $28.8 million which will be paid over approximately 10 years . ​ ​ Lease Impairment Charges ​ Long-lived assets, including operating right-of-use assets, are reviewed for impairment whenever events or changes in circumstances indicate the carrying value of an asset may not be recoverable. During the third quarter of 2023, the Company evaluated for impairment certain long-lived operating right-of-use assets that were made available for sublease. The assets evaluated for impairment included the operating right-of-use assets and leasehold improvements for a service center within the Asset-Based segment from which operations were relocated to a purchased facility; certain office spaces within the Asset-Light segment that have been vacated as a cost reduction measure in light of ongoing market changes impacting the Asset-Light business and changing employee work location trends; and certain leased facilities reported within “Other and eliminations” utilized for the service center operations of a freight handling pilot location, as operations transitioned back to the owned Asset-Based service center facility where they had previously been located, following the pause of the hardware pilot program at ABF Freight. ​ After determining the carrying values of these asset groups were not recoverable, impairment was measured and lease impairment charges were recognized for the amount by which the carrying value exceeded the fair value of the asset groups. To estimate the fair value of the asset groups, the Company relied on a discounted cash flow method utilizing market-participant discount rates estimated with Level 3 inputs (see Note C). ​ As a result of these evaluations, the Company recognized $30.2 million of lease impairment charges as a component of operating expenses in the consolidated statements of operations for the year ended December 31, 2023. The impairment losses recorded include $28.1 million related to the operating right-of-use assets with the remaining amount related to leasehold improvements. The Company determined the right-of-use assets and leasehold improvements are not or will not be abandoned, as there is a plan to sublease the properties, and the right-of-use assets will continue to be classified as held and used.

LONG-TERM DEBT AND FINANCING AR

LONG-TERM DEBT AND FINANCING ARRANGEMENTS	12 Months Ended
	Dec. 31, 2023
LONG-TERM DEBT AND FINANCING ARRANGEMENTS
LONG-TERM DEBT AND FINANCING ARRANGEMENTS	NOTE I – LONG-TERM DEBT AND FINANCING ARRANGEMENTS ​ Long-Term Debt Obligations ​ Long-term debt consisted of borrowings outstanding under the Company’s revolving credit facility, which is further described in Financing Arrangements within this Note, and notes payable related to the financing of revenue equipment (tractors and trailers used primarily in Asset-Based segment operations) and certain other equipment as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 ​ December 31 ​ ​ 2023 2022 ​ ​ (in thousands) ​ Credit Facility (interest rate of 6.6% (1) ​ $ 50,000 ​ $ 50,000 ​ Notes payable (weighted-average interest rate of 3.8% at December 31, 2023) ​ 178,938 ​ 214,623 ​ ​ ​ 228,938 ​ 264,623 ​ Less current portion ​ 66,948 ​ 66,252 ​ Long-term debt, less current portion ​ $ 161,990 ​ $ 198,371 ​ (1) The interest rate swap mitigates interest rate risk by effectively converting the $50.0 million of borrowings under the Credit Facility from variable-rate interest to fixed-rate interest with a per annum rate of 1.55% based on the margin of the Credit Facility as of December 31, 2023 and 2022, respectively. ​ Scheduled maturities of long term debt obligations as of December 31, 2023 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Credit Notes ​ ​ ​ Total ​ Facility (1) ​ Payable ​ ​ ​ (in thousands) ​ 2024 ​ $ 75,800 ​ $ 3,021 ​ $ 72,779 ​ 2025 ​ 53,388 ​ 2,353 ​ ​ 51,035 ​ 2026 ​ 41,476 ​ 2,211 ​ ​ 39,265 ​ 2027 ​ 74,972 ​ 51,688 ​ ​ 23,284 ​ 2028 ​ 5,520 ​ ​ — ​ ​ 5,520 ​ Total payments ​ 251,156 ​ 59,273 ​ ​ 191,883 ​ Less amounts representing interest ​ 22,218 ​ 9,273 ​ 12,945 ​ Long-term debt ​ $ 228,938 ​ $ 50,000 ​ $ 178,938 ​ (1) The future interest payments included in the scheduled maturities due are calculated using variable interest rates based on the SOFR swap curve, plus the anticipated applicable margin, exclusive of payments on the interest rate swap. ​ ​ Assets securing notes payable at December 31 were included in property, plant and equipment as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 ​ ​ (in thousands) Revenue equipment $ 300,922 $ 294,700 ​ Service, office, and other equipment ​ ​ 38,138 ​ ​ 41,522 ​ Total assets securing notes payable ​ 339,060 ​ 336,222 ​ Less accumulated depreciation (1) ​ 135,305 ​ 119,244 ​ Net assets securing notes payable ​ $ 203,755 ​ $ 216,978 ​ (1) Depreciation of assets securing notes payable is included in depreciation expense . ​ The Company’s long-term debt obligations have a weighted-average interest rate of 3.3% at December 31, 2023. The Company paid interest of $8.7 million, $7.1 million, and $8.7 million in 2023, 2022, and 2021, respectively, net of capitalized interest which totaled $0.3 million, $0.3 million, and $0.5 million for 2023, 2022, and 2021, respectively. ​ Financing Arrangements ​ Credit Facility The Company has a revolving credit facility (the “Credit Facility”) under its Fourth Amended and Restated Credit Agreement (the “Credit Agreement”), which was amended and restated in October 2022. The amendment, among other things, increased the aggregate amount of the swing line facility from $25.0 million to $40.0 million, extended the scheduled maturity date from October 1, 2024 to October 7, 2027, replaced LIBOR-based interest pricing conventions with interest pricing based on the SOFR, released the liens on the assets of the Company and certain subsidiaries, and released pledges of equity interests in certain subsidiaries. As a result of the amendment, the Credit Facility is now an unsecured facility. However, the indebtedness under the Credit Agreement and certain other obligations owed to lenders or their affiliates are cross-guaranteed by the Company and certain subsidiaries. ​ The Credit Facility has an initial maximum credit amount of $250.0 million, including a swing line facility in an aggregate amount of up to $40.0 million and a letter of credit sub-facility providing for the issuance of letters of credit up to an aggregate amount of $20.0 million. The Company may request additional revolving commitments or incremental term loans thereunder up to an aggregate amount of up to $125.0 million, subject to the satisfaction of certain additional conditions as provided in the Credit Agreement. As of December 31, 2023, the Company had available borrowing capacity of $200.0 million under the initial maximum credit amount of the Credit Facility. ​ Principal payments under the Credit Facility are due upon maturity of the facility on October 7, 2027; however, borrowings may be repaid, at the Company’s discretion, in whole or in part at any time, without penalty, subject to required notice periods and compliance with minimum prepayment amounts. Borrowings under the Credit Agreement can either be, at the Company’s election: (i) at an Alternate Base Rate (as defined in the Credit Agreement) plus a spread ranging from 0.125% to 1.00%, and SOFR adjustment of 0.10% per annum; or (ii) the Adjusted Term SOFR Screen Rate (as defined in the Credit Agreement) plus a spread ranging from 1.125% to 2.00%. The applicable spread is dependent upon the Company’s Adjusted Leverage Ratio (as defined in the Credit Agreement). In addition, the Credit Facility requires the Company to pay a fee on unused commitments. The Credit Agreement contains conditions, representations and warranties, events of default, and indemnification provisions that are customary for financings of this type, including, but not limited to, a minimum interest coverage ratio, a maximum adjusted leverage ratio, and limitations on incurrence of debt, investments, liens on assets, certain sale and leaseback transactions, transactions with affiliates, mergers, consolidations, and sales of assets. The Company was in compliance with the covenants under the Credit Agreement at December 31, 2023. ​ Interest Rate Swap As noted in the table above, the Company has an interest rate swap agreement with a $50.0 million notional amount, which started on June 30, 2022 and will end on October 1, 2024. The interest rate swap agreement was amended in October 2022 to replace LIBOR-based interest pricing conventions with interest pricing based on the SOFR. Under the amended interest rate swap agreement, the Company receives floating-rate interest amounts based on one-month SOFR in exchange for fixed-rate interest payments of 0.33% throughout the remaining term of the agreement. The fair value of the interest rate swap of $1.7 million and $3.5 million was recorded in other long-term assets at December 31, 2023 and 2022, respectively. The interest rate swap continues to qualify for cash flow hedge accounting through application of expedients provided for contracts affected by reference rate reform. Remeasurement at the modification date or reassessment from the previous accounting determination was not required. ​ The unrealized gain or loss on the interest rate swap instruments in effect at the balance sheet date was reported as a component of accumulated other comprehensive income, net of tax, in stockholders’ equity at December 31, 2023 and 2022, and the change in the unrealized gain or loss on the interest rate swap for the years ended December 31, 2023 and 2022 was reported in other comprehensive income (loss), net of tax, in the consolidated statements of comprehensive income. The interest rate swap is subject to certain customary provisions that could allow the counterparty to request immediate settlement of the fair value liability or asset upon violation of any or all of the provisions. The Company was in compliance with all provisions of the interest rate swap agreement at December 31, 2023. ​ Accounts Receivable Securitization Program The Company’s accounts receivable securitization program, which matures on July 1, 2024, provides available cash proceeds of $50.0 million under the program and has an accordion feature allowing the Company to request additional borrowings up to $100.0 million, subject to certain conditions. In May 2022, the Company amended its accounts receivable securitization program to, among other things, increase certain ratios, including the delinquency, default, and accounts receivable turnover ratios, as defined in the agreement; add language addressing the potential inclusion of receivables originated by MoLo; and replace LIBOR-based interest pricing conventions with interest pricing based on the SOFR. The program ratios were adjusted to accommodate revenue growth and customer demand for integrated logistics solutions, which has resulted in an increased proportion of total revenues generated by the Company’s Asset-Light operations and, as a result, longer collection periods on the Company’s accounts receivable, as are typical for asset-light businesses. ​ Under this program, certain subsidiaries of the Company continuously sell a designated pool of trade accounts receivables to a wholly owned subsidiary which, in turn, may borrow funds on a revolving basis. This wholly owned consolidated subsidiary is a separate bankruptcy-remote entity, and its assets would be available only to satisfy the claims related to the lender’s interest in the trade accounts receivables. Borrowings under the amended accounts receivable securitization program bear interest based upon SOFR, plus a margin, and an annual facility fee. The securitization agreement contains representations and warranties, affirmative and negative covenants, and events of default that are customary for financings of this type, including a maximum adjusted leverage ratio covenant. The Company was in compliance with the covenants under the accounts receivable securitization program at December 31, 2023. ​ The accounts receivable securitization program includes a provision under which the Company may request and the letter of credit issuer may issue standby letters of credit, primarily in support of workers’ compensation and third-party casualty claims liabilities in various states in which the Company is self-insured. The outstanding standby letters of credit reduce the availability of borrowings under the program. As of December 31, 2023, standby letters of credit of $16.8 million have been issued under the program, which reduced the available borrowing capacity to $33.2 million. ​ Letter of Credit Agreements and Surety Bond Programs As of both December 31, 2023 and 2022, the Company had letters of credit outstanding of $17.4 million and $10.6 million, respectively (including $16.8 million and $10.0 million, respectively issued under the accounts receivable securitization program). The Company has programs in place with multiple surety companies for the issuance of surety bonds in support of its self-insurance program. As of December 31, 2023 and 2022, surety bonds outstanding related to the self-insurance program totaled $65.2 million and $62.6 million, respectively. ​ Notes Payable The Company has financed the purchase of certain revenue equipment, other equipment, and software through promissory note arrangements. During the year ended December 31, 2023 and 2022, the Company entered into notes payable arrangements, primarily for revenue equipment, of $33.5 million and $82.4 million, respectively.

ACCRUED EXPENSES

ACCRUED EXPENSES	12 Months Ended
	Dec. 31, 2023
ACCRUED EXPENSES.
ACCRUED EXPENSES	NOTE J – ACCRUED EXPENSES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 ​ ​ 2023 2022 ​ ​ ​ (in thousands) ​ Workers’ compensation, third-party casualty, and loss and damage claims reserves ​ $ 189,948 ​ $ 133,122 ​ Accrued vacation pay ​ 63,183 ​ 58,875 ​ Accrued compensation, including retirement benefits ​ ​ 87,851 ​ ​ 119,836 ​ Taxes other than income ​ 10,743 ​ 11,375 ​ Other ​ 26,304 ​ 15,249 ​ Total accrued expenses ​ $ 378,029 ​ $ 338,457 ​ ​

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	12 Months Ended
	Dec. 31, 2023
POSTRETIREMENT BENEFIT PLANS
EMPLOYEE BENEFIT PLANS	NOTE K – EMPLOYEE BENEFIT PLANS ​ Supplemental Benefit and Postretirement Health Benefit Plans ​ The Company has an unfunded supplemental benefit plan (the “SBP”) which was designed to supplement benefits under the Company’s legacy nonunion defined benefit pension plan (for which plan termination and liquidation was completed in 2019) for designated executive officers. The SBP was closed to new entrants, and a cap was placed on the maximum payment per participant in the SBP effective January 1, 2006. In place of the SBP, eligible officers of the Company appointed after 2005 participate in a long-term cash incentive plan (see Cash Long-Term Incentive Compensation Plan section within this Note). Effective December 31, 2009, the accrual of benefits for remaining participants under the SBP was frozen. With the exception of early retirement penalties that may apply in certain cases, the valuation inputs for calculating the frozen SBP benefits to be paid to participants, including final average salary and the interest rate, were frozen at December 31, 2009. The SBP did not incur pension settlement expense in 2023, 2022, or 2021. ​ The Company sponsors an insured postretirement health benefit plan that provides supplemental medical benefits and dental and vision benefits primarily to certain officers of the Company and certain subsidiaries. New entrants have not been added to the postretirement health benefit plan since January 1, 2017. ​ The following table discloses the changes in benefit obligations and plan assets of the Company’s nonunion defined benefit plans for years ended December 31, the measurement date of the plans: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2023 2022 2023 2022 ​ ​ (in thousands) Change in benefit obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Benefit obligations, beginning of year ​ $ 338 ​ $ 381 ​ $ 12,534 ​ $ 16,992 ​ Service cost ​ — ​ — ​ 78 ​ 156 ​ Interest cost ​ 16 ​ 7 ​ 599 ​ 441 ​ Actuarial (gain) loss (1) ​ 4 ​ (50) ​ 1,137 ​ (4,392) ​ Benefits paid ​ — ​ — ​ (680) ​ (663) ​ Benefit obligations, end of year ​ 358 ​ 338 ​ 13,668 ​ 12,534 ​ Change in plan assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value of plan asset, beginning of year ​ — ​ — ​ — ​ — ​ Employer contributions ​ — ​ — ​ 680 ​ 663 ​ Benefits paid ​ — ​ — ​ (680) ​ (663) ​ Fair value of plan assets, end of year ​ — ​ — ​ — ​ — ​ Funded status at period end ​ $ (358) ​ $ (338) ​ $ (13,668) ​ $ (12,534) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated benefit obligation ​ $ 358 ​ $ 338 ​ $ 13,668 ​ $ 12,534 ​ (1) The actuarial losses on the SBP and postretirement health benefit plan for 2023 were primarily related to decreases in the discount rates used to remeasure the plans’ obligations at December 31, 2023 versus the prior year, and the actuarial gains for 2022 were primarily related to increases in the discount rates used in the remeasurement at December 31, 2022. ​ Amounts recognized in the consolidated balance sheets at December 31 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2023 2022 2023 2022 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current portion of pension and postretirement liabilities ​ $ — ​ $ — ​ $ (707) ​ $ (676) ​ Pension and postretirement liabilities, less current portion ​ (358) ​ (338) ​ (12,961) ​ (11,858) ​ Liabilities recognized ​ $ (358) ​ $ (338) ​ $ (13,668) ​ $ (12,534) ​ ​ The following is a summary of the components of net periodic benefit cost for the Company’s nonunion benefit plans for the years ended December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ ​ Benefit Plan ​ Health Benefit Plan ​ ​ 2023 2022 2021 2023 2022 2021 ​ ​ (in thousands) ​ Service cost ​ $ — ​ $ — ​ $ — ​ $ 78 ​ $ 156 ​ $ 192 ​ Interest cost ​ 16 ​ 7 ​ 4 ​ 599 ​ 441 ​ 427 ​ Amortization of net actuarial (gain) loss (1) ​ (4) ​ 8 ​ 9 ​ (1,326) ​ (765) ​ (548) ​ Net periodic benefit cost (credit) ​ $ 12 ​ $ 15 ​ $ 13 ​ $ (649) ​ $ (168) ​ $ 71 ​ (1) The Company amortizes actuarial gains and losses over the average remaining active service period of the plan participants and does not use a corridor approach. ​ Included in accumulated other comprehensive loss at December 31 were the following pre-tax amounts that have not yet been recognized in net periodic benefit cost: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2023 2022 2023 2022 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net actuarial gain ​ $ (9) ​ $ (18) ​ $ (6,806) ​ $ (9,269) ​ ​ The discount rate is determined by matching projected cash distributions with appropriate high-quality corporate bond yields in a yield curve analysis. Weighted-average assumptions used to determine nonunion benefit obligations at December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2023 2022 2023 2022 Discount rate ​ 4.3 % 4.6 % 4.8 % 5.0 % ​ Weighted-average assumptions used to determine net periodic benefit cost for the Company’s nonunion benefit plans for the years ended December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2023 2022 2021 2023 2022 2021 Discount rate ​ 4.6 % 1.8 % 1.1 % 5.0 % 2.7 % 2.3 % ​ The assumed health care cost trend rates for the Company’s postretirement health benefit plan at December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Health care cost trend rate assumed for next year (1) ​ 7.0 % 7.0 % Rate to which the cost trend rate is assumed to decline ​ 4.5 % 4.5 % Year that the rate reaches the cost trend assumed rate 2035 2034 (1) At each December 31 measurement date, health care cost rates for the following year are based on known premiums for the fully insured postretirement health benefit plan. Therefore, the first year of assumed health care cost trend rates presented as of December 31, 2023 and 2022 are for 2025 and 2024, respectively. ​ Estimated future benefit payments from the Company’s SBP and postretirement health benefit plans, which reflect expected future service as appropriate, as of December 31, 2023 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental Postretirement ​ ​ Benefit ​ Health ​ ​ Plan ​ Benefit Plan ​ ​ ​ ​ ​ ​ ​ 2024 ​ $ — ​ $ 707 ​ 2025 ​ $ — ​ $ 744 ​ 2026 ​ $ — ​ $ 747 ​ 2027 ​ $ — ​ $ 754 ​ 2028 ​ $ 424 ​ $ 761 ​ 2029-2033 ​ $ — ​ $ 3,836 ​ ​ Deferred Compensation Plans ​ The Company has deferred salary agreements with certain executives for which liabilities of $1.1 million and $1.3 million were recorded as of December 31, 2023 and 2022, respectively. The deferred salary agreements include a provision that immediately vests all benefits and provides for a lump-sum payment upon a change in control of the Company that is followed by a termination of the executive. The deferred salary agreement program was closed to new entrants effective January 1, 2006. In place of the deferred salary agreement program, officers appointed after 2005 participate in the Long-Term Incentive Plan (see Long-Term Incentive Compensation Plan section within this Note). ​ The Company maintains a Voluntary Savings Plan (“VSP”), a nonqualified deferred compensation program for the benefit of certain executives of the Company and certain subsidiaries. Eligible employees may defer receipt of a portion of their salary and incentive compensation into the VSP by making an election prior to the beginning of the year in which the salary compensation is payable and, for incentive compensation, by making an election at least six months prior to the end of the performance period to which the incentive relates. The Company credits participants’ accounts with applicable rates of return based on a portfolio selected by the participants from the investments available in the plan. The Company match related to the VSP was suspended beginning January 1, 2010. All deferrals, Company match, and investment earnings are considered part of the general assets of the Company until paid. Accordingly, the consolidated balance sheets reflect the fair value of the aggregate participant balances, based on quoted prices of the mutual fund investments, as both an asset and a liability of the Company. As of December 31, 2023 and 2022, VSP balances of $4.6 million and $4.0 million, respectively, were included in other long-term assets liabilities ​ Defined Contribution Plans ​ The Company and its subsidiaries have defined contribution 401(k) plans that cover substantially all nonunion employees. The plans permit participants to defer a portion of their salary up to a maximum of 69% as determined under Section 401(k) of the IRC. For certain participating subsidiaries, the Company matches 50% of nonunion participant contributions up to the first 6% of annual compensation. The Company’s matching expense for the nonunion 401(k) plans totaled $7.1 million, $9.4 million, and $7.7 million for 2023, 2022, and 2021, respectively. The plans also allow for discretionary 401(k) Company contributions determined annually. The Company recognized expense of $13.1 million, $19.1 million, and $16.8 million in 2023, 2022, and 2021, respectively, related to its discretionary contributions to the nonunion defined contribution 401(k) plans. Discretionary contribution expense was higher in 2022, primarily due to an increase in discretionary contribution rate based on the Company’s higher operating results for the year. Participants are fully vested in the Company’s contributions under the defined contribution 401(k) plans after three years of service. ​ Long-Term Incentive Compensation Plan ​ The Company maintains a performance-based Long-Term Incentive Compensation Plan (“LTIP”) for certain officers of the Company or its subsidiaries. The LTIP incentive, which is earned over three years, is based, in part, upon a proportionate weighting of return on capital employed and shareholder returns compared to a peer group, as specifically defined in the plan document. As of December 31, 2023, 2022, and 2021, $26.3 million, $29.5 million, $28.3 million, respectively, were accrued for future payments under the plans. ​ Other Plans ​ Other long-term assets include $48.5 million and $54.7 million at December 31, 2023 and 2022, respectively, in the cash surrender value of life insurance policies. These policies are intended to provide funding for certain of the Company’s long-term nonunion benefit plans. A portion of the Company’s cash surrender value of variable life insurance policies have investments, through separate accounts, in equity and fixed income securities and, therefore, are subject to market volatility. The Company recognized a gain of $4.6 million for 2023, a loss of $2.7 million 2022, and a gain of $4.1 million for 2021, associated with changes in the cash surrender value and proceeds from life insurance policies. ​ Multiemployer Plans ​ ABF Freight System, Inc. and certain other subsidiaries reported in the Company’s Asset-Based operating segment (“ABF Freight”) contribute to multiemployer pension and health and welfare plans, which have been established pursuant to the Labor Management Relations Act of 1947 ​ The multiemployer plans to which ABF Freight primarily contributes are jointly trusteed (half of the trustees of each plan are selected by the participating employers, the other half by the IBT) and cover collectively bargained employees of multiple unrelated employers. Due to the inherent nature of multiemployer plans, there are risks associated with participation in these plans that differ from single employer plans. Assets received by the plans are not segregated by employer, and contributions made by one employer can be and are used to provide benefits to current and former employees of other employers. If a participating employer in a multiemployer pension plan no longer contributes to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers. If a participating employer in a multiemployer pension plan completely withdraws from the plan, it owes to the plan its proportionate share of the plan’s unfunded vested benefits, referred to as a withdrawal liability. A complete withdrawal generally occurs when the employer permanently ceases to have an obligation to contribute to the plan. Withdrawal liability is also owed in the event the employer withdraws from a plan in connection with a mass withdrawal, which generally occurs when all or substantially all employers withdraw from the plan pursuant to an agreement in a relatively short period of time. Were ABF Freight to completely withdraw from certain multiemployer pension plans, whether in connection with a mass withdrawal or otherwise, under current law, ABF Freight would have material liabilities for its share of the unfunded vested liabilities of each such plan. ​ Pension Plans The 25 multiemployer pension plans to which ABF Freight contributes vary greatly in size and in funded status. Contributions to these plans are based generally on the time worked by ABF Freight’s contractual employees, at rates specified in the 2023 ABF NMFA, which will remain in effect through June 30, 2028. The funding obligations to the pension plans are intended to satisfy the requirements imposed by the Pension Protection Act of 2006 Multiemployer Pension Reform Act of 2014 Consolidated and Further Continuing Appropriations Act of 2015 ​ The PPA requires that “endangered” (generally less than 80% funded and commonly called “yellow zone”) plans adopt “funding improvement plans” and that “critical” (generally less than 65% funded and commonly called “red zone”) plans adopt “rehabilitation plans” that are intended to improve the plan’s funded status over time. The Reform Act includes provisions to address the funding of multiemployer pension plans in “critical and declining” status, including certain of those in which ABF Freight participates. Critical and declining status is applicable to critical status plans that are projected to become insolvent anytime within the next 14 plan years, or if the plan is projected to become insolvent within the next 19 plan years and either the plan’s ratio of inactive participants to active participants exceeds two to one or the plan’s funded percentage is less than 80%. Provisions of the Reform Act include, among others, providing qualifying plans the ability to self - ​ On March 11, 2021, H.R.1319, the American Rescue Plan Act of 2021 Butch Lewis Emergency Pension Plan Relief Act of 2021 ​ On July 9, 2021, the PBGC announced an interim final rule implementing a Special Financial Assistance Program (the “SFA Program”) to administer funds to severely underfunded eligible multiemployer pension plans under the Pension Relief Act. Certain multiemployer pension plans to which ABF Freight contributes, including the Central States, Southeast and Southwest Areas Pension Plan (the “Central States Pension Plan”), have applied for or received funds under the SFA Program which could allow them to avoid insolvency and improve their funded status. Under the American Rescue Plan Act and in accordance with regulations of the PBGC, the plans receiving funding under the SFA Program are not permitted to reduce employer contributions to their funds. The Company will continue to evaluate the impact of the assistance provided by the SFA Program on ABF Freight’s multiemployer pension plan contributions. Through the term of the 2023 ABF NMFA, ABF Freight’s multiemployer pension contribution obligations generally will be satisfied by making the specified contributions when due. Future contribution rates will be determined through the negotiation process for contract periods following the term of the current collective bargaining agreement. While the Company cannot determine with any certainty the contributions that will be required under future collective bargaining agreements for ABF Freight’s contractual employees, management believes future contribution rates to multiemployer pension plans may be less likely to increase as a result of the provisions of the Pension Relief Act. ​ Based on the most recent funding information the Company has received, approximately 6% of ABF Freight’s multiemployer pension plan contributions for the year ended December 31, 2023 were made to plans that are in “critical and declining status;” approximately 53% were made to plans that are in “critical status,” including the Central States Pension Plan discussed below; and no contributions were made to plans that are in “endangered status,” each as defined by the PPA. ABF Freight’s participation in multiemployer pension plans is summarized in the table below. The multiemployer pension plans listed separately in the table represent plans that are individually significant to the Asset-Based segment based on the amount of plan contributions. The Central States Pension Plan is the only fund individually listed in the table which received financial assistance from the SFA Program. The severity of a plan’s underfunded status considered in the analysis of individually significant funds to be separately disclosed was after the financial assistance from the SFA Program. ​ Significant multiemployer pension funds and key participation information were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension ​ FIP/RP ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Protection Act ​ Status ​ Contributions (d) ​ ​ ​ ​ EIN/Pension ​ Zone Status (b) ​ Pending/ ​ (in thousands) ​ Surcharge Legal Name of Plan Plan Number (a) 2023 2022 Implemented (c) 2023 2022 2021 Imposed (e) Central States, Southeast and Southwest Areas Pension Plan (1)(2) 36-6044243 Critical Critical and Declining Implemented (3) ​ $ 77,708 ​ $ 75,306 ​ $ 71,045 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Western Conference of Teamsters Pension Plan (4) 91-6145047 Green Green No ​ 29,540 ​ 28,051 ​ 25,861 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Central Pennsylvania Teamsters Defined Benefit Plan (1)(4) 23-6262789 Green Green No ​ 15,540 ​ 14,421 ​ 13,931 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ I. B. of T. Union Local No. 710 Pension Fund (5)(6) 36-2377656 Green (7) Green (7) No ​ 10,676 ​ 9,838 ​ 9,553 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ New England Teamsters Pension Fund (8)(9) 04-6372430 Critical and Declining (10) Critical and Declining (10) Implemented (11) ​ 4,636 ​ 4,449 ​ 4,357 ​ No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ All other plans in the aggregate ​ ​ ​ ​ ​ ​ ​ ​ ​ 24,384 ​ 22,493 ​ 22,146 ​ ​ Total multiemployer pension contributions paid (12) ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 162,484 ​ $ 154,558 ​ $ 146,893 ​ ​ Table Heading Definitions ​ (a) The “EIN/Pension Plan Number” column provides the Federal Employer Identification Number (“EIN”) and the three-digit plan number, if applicable. (b) Unless otherwise noted, the most recent PPA zone status available in 2023 and 2022 is for the plan’s year-end status at December 31, 2022 and 2021, respectively, and prior to financial assistance from the Pension Relief Act. The zone status is based on information received from the plan and was certified by the plan’s actuary. Green zone funds are those that are in neither endangered, critical, or critical and declining status and generally have a funded percentage of at least 80% . (c) The “FIP/RP Status Pending/Implemented” column indicates if a funding improvement plan (“FIP”) or a rehabilitation plan (“RP”), if applicable, is pending or has been implemented. (d) Amounts reflect contributions made in the respective year and differ from amounts expensed during the year. (e) The surcharge column indicates if a surcharge was paid by ABF Freight to the plan. ​ Table Footnotes ​ (1) ABF Freight System, Inc. was listed by the plan as providing more than 5% of the total contributions to the plan for the plan years ended December 31, 2022 and 2021. (2) Information for this fund was obtained from the 2022 annual funding notice, other notices received from the plan such as the 2023 notice of critical status, and the Form 5500 filed for the plan years ended December 31, 2022 and 2021. (3) Adopted a rehabilitation plan effective March 25, 2008 as updated. Utilized amortization extension granted by the IRS effective December 31, 2003. (4) Information for this fund was obtained from the annual funding notice, other notices received from the plan, and the Form 5500 filed for the plan years ended December 31, 2022 and 2021. (5) The Company was listed by the plan as providing more than 5% of the total contributions to the plan for the plan year ended January 31, 2023. (6) Information for this fund was obtained from the annual funding notice, other notices received from the plan, and the Form 5500 filed for the plan years ended January 31, 2023 and 2022. (7) PPA zone status relates to plan years February 1, 2022 – January 31, 2023 and February 1, 2021 – January 31, 2022. (8) Contributions include $1.6 million each year for 2023, 2022, and 2021, related to the multiemployer pension fund withdrawal liability. ABF Freight’s multiemployer pension plan obligation with the New England Teamsters and Trucking Industry Pension Fund was restructured under a transition agreement effective on August 1, 2018, which triggered a withdrawal liability settlement to satisfy ABF Freight’s existing potential withdrawal liability obligation to the fund. ABF Freight recognized a one-time charge of $37.9 million (pre-tax) to record the withdrawal liability in second quarter 2018; partially settled the withdrawal liability through the initial lump sum cash payment of $15.1 million made in third quarter 2018; and will settle the remainder with monthly payments over a remaining period of 18 years . (9) Information for this fund was obtained from the annual funding notice, other notices received from the plan, and the Form 5500 filed for the plan years ended September 30, 2022 and 2021. (10) PPA zone status relates to plan years October 1, 2022 – September 30, 2023 and October 1, 2021 – September 30, 2022. (11) Adopted a rehabilitation plan effective January 1, 2009. The plan has been subsequently reviewed and restated effective January 1, 2023. (12) Contribution levels can be impacted by several factors such as changes in business levels and the related time worked by contractual employees, contractual rate increases for pension benefits, and the specific funding structure, which differs among funds. The current and prior collective bargaining agreements and the related supplemental agreements provided for contributions to multiemployer pension plans to be frozen at the current rates for each fund, although certain funds have imposed contribution increases under their rehabilitation or funding improvement plans. The year-over-year changes in multiemployer pension plan contributions presented above were influenced by changes in Asset-Based shipment levels. ​ For 2023, 2022, and 2021, approximately one-half of ABF Freight’s multiemployer pension contributions were made to the Central States Pension Plan. The funded percentages of the Central States Pension Plan, as set forth in information provided by the Central States Pension Plan, were 14.5%, and 17.1% as of January 1, 2022 and 2021, respectively. ABF Freight received a Notice of Critical Status for the Central States Pension Plan dated March 31, 2023, in which the plan’s actuary certified that, as of January 1, 2023 the approximate funding percentage was 97.5%; however, the plan is deemed to be in critical status through 2051 due to the receipt of funding from the SFA Program in January 2023. The plan announced that the SFA Program funding will allow the Central States Pension Plan to avoid insolvency in 2025 and to reach full funding over time. ​ The funding notices for the 2022 plan year for the Western Pennsylvania Teamsters and Employers Pension Fund, the New York State Teamsters Conference Pension and Retirement Fund, and the Trucking Employees of North Jersey Welfare Fund, Inc. – Pension Fund reflected the reinstatement of benefits previously suspended due to the significantly improved status of each fund due to the funding provided by the SFA Program; however, these funds will be deemed to be in critical status through the end of 2051. The Company also previously received notice that the PBGC will provide financial assistance (by paying retiree benefits not to exceed the PBGC guarantee limits) to the Road Carriers Local 707 Pension Fund, which was declared insolvent; however, this fund received SFA Program funding during 2022. Approximately 1% to 2% of ABF Freight’s total multiemployer pension contributions for the year ended December 31, 2023 were made to each of these funds. ​ ABF Freight has not received any other notification of plan reorganization or plan insolvency with respect to any multiemployer pension plan to which it contributes. ​ Health and Welfare Plans ABF Freight contributes to 38 multiemployer health and welfare plans which provide health care benefits for active employees and retirees covered under labor agreements. Contributions to multiemployer health and welfare plans totaled $215.6 million, $194.4 million, and $176.2 million, for the year ended December 31, 2023, 2022, and 2021, respectively. The benefit contribution rate for health and welfare benefits increased by an average of approximately 5.7% on August 1, 2023 under ABF Freight’s current collective bargaining agreement with IBT ratified in 2023 and 4.3% on both August 1, 2022 and 2021 under ABF Freight’s prior collective bargaining agreement with the IBT ratified in 2018. ​ Higher benefit contribution rates following the 2023 ABF NMFA ratification and more hours worked to maintain capacity in the first half of the year and to service higher business levels in the second half of the year, resulted in an increase in contributions to health and welfare plans in 2023, compared to 2022. In 2022, more hours worked by ABF Freight’s contractual employees, as well as the hiring of additional contractual employees to service higher shipment levels resulted in an increase in contributions to multiemployer health and welfare plans in 2022, compared to 2021. Other than changes to benefit contribution rates and variances in rates and time worked, there have been no other significant items that affect the comparability of the Company’s 2023, 2022, and 2021 multiemployer health and welfare plan contributions.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
	Dec. 31, 2023
STOCKHOLDERS' EQUITY
STOCKHOLDERS' EQUITY	​ ​ NOTE L – STOCKHOLDERS’ EQUITY ​ Accumulated Other Comprehensive Income ​ Components of accumulated other comprehensive income were as follows at December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands) Pre-tax amounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net periodic benefit credit ​ $ 6,816 ​ $ 9,287 ​ $ 5,602 ​ Interest rate swap ​ ​ 1,710 ​ ​ 3,526 ​ ​ 419 ​ Foreign currency translation ​ (2,709) ​ (3,247) ​ (1,044) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ $ 5,817 ​ $ 9,566 ​ $ 4,977 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ After-tax amounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net periodic benefit credit ​ $ 5,061 ​ $ 6,896 ​ $ 4,160 ​ Interest rate swap ​ ​ 1,263 ​ ​ 2,604 ​ ​ 309 ​ Foreign currency translation ​ (2,000) ​ (2,397) ​ (770) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ $ 4,324 ​ $ 7,103 ​ $ 3,699 ​ ​ ​ The following is a summary of the changes in accumulated other comprehensive income, net of tax, by component: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized ​ ​ Interest Foreign ​ ​ ​ ​ ​ ​ Net Periodic ​ ​ Rate ​ Currency ​ ​ Total Benefit Credit ​ Swap Translation ​ ​ ​ (in thousands) ​ Balances at December 31, 2021 ​ $ 3,699 ​ $ 4,160 ​ $ 309 ​ $ (770) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive income (loss) before reclassifications ​ ​ 3,966 ​ ​ 3,298 ​ ​ 2,295 ​ ​ (1,627) ​ Amounts reclassified from accumulated other comprehensive income ​ ​ (562) ​ ​ (562) ​ ​ — ​ ​ — ​ Net current-period other comprehensive income (loss) ​ ​ 3,404 ​ ​ 2,736 ​ ​ 2,295 ​ ​ (1,627) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balances at December 31, 2022 ​ $ 7,103 ​ $ 6,896 ​ $ 2,604 ​ $ (2,397) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive income (loss) before reclassifications ​ (1,791) ​ (847) ​ ​ (1,341) ​ 397 ​ Amounts reclassified from accumulated other comprehensive income ​ (988) ​ (988) ​ ​ — ​ — ​ Net current-period other comprehensive income (loss) ​ (2,779) ​ (1,835) ​ ​ (1,341) ​ 397 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balances at December 31, 2023 ​ $ 4,324 ​ $ 5,061 ​ $ 1,263 ​ $ (2,000) ​ ​ ​ The following is a summary of the significant reclassifications out of accumulated other comprehensive income by component for the years ended December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized Net Periodic ​ ​ ​ Benefit Credit ​ 2023 2022 ​ ​ (in thousands) Amortization of net actuarial gain, pre-tax (1) ​ $ 1,330 ​ $ 757 ​ Tax expense ​ ​ (342) ​ (195) ​ Total, net of tax ​ $ 988 ​ $ 562 ​ (1) Included in the computation of net periodic benefit credit of the Company’s supplemental benefit plan (“SBP”) and postretirement health benefit plan (see Note K). ​ Dividends on Common Stock ​ The following table is a summary of dividends declared during the applicable quarter: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 ​ 2022 ​ ​ Per Share Amount Per Share Amount ​ ​ (in thousands, except per share data) First quarter ​ $ 0.12 ​ $ 2,915 ​ $ 0.08 ​ $ 1,978 ​ Second quarter ​ $ 0.12 ​ $ 2,894 ​ $ 0.12 ​ $ 2,949 ​ Third quarter ​ $ 0.12 ​ $ 2,887 ​ $ 0.12 ​ $ 2,965 ​ Fourth quarter ​ $ 0.12 ​ $ 2,846 ​ $ 0.12 ​ $ 2,938 ​ ​ On February 2, 2024, the Company’s Board of Directors declared a dividend of $0.12 per share to stockholders of record as of February 16, 2024. ​ Treasury Stock ​ The Company has a program to repurchase its common stock in the open market or in privately negotiated transactions (the “share repurchase program”). The share repurchase program has no expiration date but may be terminated at any time at the Board of Directors’ discretion. Repurchases may be made using the Company’s cash reserves or other available sources. ​ In February 2023, the Board of Directors reauthorized the share repurchase program and increased the total amount available for purchases of the Company’s common stock under the program to $125.0 million. During 2023, the Company purchased 930,754 shares of its common stock for an aggregate cost of $91.5 million, including 501,146 shares for an aggregate cost of $47.6 million under Rule 10b5-1 plans, which allowed for stock repurchases during closed trading windows. The Company had $33.5 million remaining under its share repurchase program as of December 31, 2023. Treasury shares totaled 6,460,137 and 5,529,383 as of December 31, 2023 and 2022, respectively. In February 2024, the Board of Directors reauthorized the share repurchase program and increased the total amount available for purchases of the Company’s common stock under the program to $125.0 million. Subsequent to December 31, 2023 through February 19, 2024, the Company settled repurchases of 51,220 shares for an aggregate cost of $6.1 million.

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2023
SHARE-BASED COMPENSATION
SHARE-BASED COMPENSATION	​ ​ NOTE M – SHARE-BASED COMPENSATION ​ Stock Awards ​ The Company had outstanding RSUs granted under the ArcBest Corporation Ownership Incentive Plan (the “Ownership Incentive Plan”) as of December 31, 2023 and 2022. The Ownership Incentive Plan provides for the granting of 4.9 million shares, which may be awarded as incentive and nonqualified stock options, stock appreciation rights, restricted stock, RSUs, or performance award units. ​ Restricted Stock Units ​ A summary of the Company’s RSU award program is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Grant Date ​ ​ ​ Units ​ Fair Value Outstanding – January 1, 2023 ​ 1,023,251 ​ $ 38.83 ​ Granted ​ 149,350 ​ $ 86.53 ​ Vested ​ (381,724) ​ $ 36.04 ​ Forfeited (1) ​ (65,444) ​ $ 51.97 ​ Outstanding – December 31, 2023 ​ 725,433 ​ $ 48.94 ​ (1) Forfeitures are recognized as they occur. ​ The Compensation Committee of the Company’s Board of Directors granted RSUs during the years ended December 31 as follows: ​ k ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Grant Date ​ Units Fair Value 2023 149,350 ​ $ 86.53 ​ 2022 164,739 ​ $ 78.57 ​ 2021 136,295 ​ $ 86.96 ​ ​ The fair value of restricted stock awards that vested in 2023, 2022, and 2021 was $34.2 million, $48.1 million, and $36.4 million, respectively. Unrecognized compensation cost related to restricted stock awards outstanding as of December 31, 2023 was $14.0 million, which is expected to be recognized over a weighted-average period of approximately 0.9 years.

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
	Dec. 31, 2023
EARNINGS PER SHARE
EARNINGS PER SHARE	NOTE N – EARNINGS PER SHARE ​ The following table sets forth the computation of basic and diluted earnings per share for the years ended December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands, except share and per share data) Basic ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income from continuing operations ​ $ 142,164 ​ $ 294,648 ​ $ 210,459 ​ Net income from discontinued operations ​ 53,269 ​ 3,561 ​ 3,062 ​ Net income ​ $ 195,433 ​ $ 298,209 ​ $ 213,521 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares ​ 24,018,801 ​ 24,585,205 ​ 25,471,939 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic earnings per common share ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Continuing operations ​ $ 5.92 ​ $ 11.98 ​ $ 8.26 ​ Discontinued operations ​ ​ 2.22 ​ ​ 0.14 ​ ​ 0.12 ​ Total basic earnings per common share (1) ​ $ 8.14 ​ $ 12.13 ​ $ 8.38 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income from continuing operations ​ $ 142,164 ​ $ 294,648 ​ $ 210,459 ​ Net income from discontinued operations ​ 53,269 ​ 3,561 ​ 3,062 ​ Net income ​ $ 195,433 ​ $ 298,209 ​ $ 213,521 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares ​ ​ 24,018,801 ​ 24,585,205 ​ 25,471,939 ​ Effect of dilutive securities ​ 615,816 ​ 919,303 ​ 1,300,187 ​ Adjusted weighted-average shares and assumed conversions ​ 24,634,617 ​ 25,504,508 ​ 26,772,126 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted earnings per common share ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Continuing operations ​ $ 5.77 ​ $ 11.55 ​ $ 7.86 ​ Discontinued operations ​ ​ 2.16 ​ ​ 0.14 ​ ​ 0.11 ​ Total diluted earnings per common share (1) ​ $ 7.93 ​ $ 11.69 ​ $ 7.98 ​ (1) Earnings per common share is calculated in total and may not equal the sum of earnings per common share from continuing operations and discontinued operations due to rounding. ​

OPERATING SEGMENT DATA

OPERATING SEGMENT DATA	12 Months Ended
	Dec. 31, 2023
OPERATING SEGMENT DATA
OPERATING SEGMENT DATA	NOTE O – OPERATING SEGMENT DATA ​ The Company uses the “management approach” to determine its reportable operating segments, as well as to determine the basis of reporting the operating segment information. The management approach focuses on financial information that the Company’s management uses to make operating decisions. Management uses revenues, operating expense categories, operating ratios, operating income (loss), and key operating statistics to evaluate performance and allocate resources to the Company’s operations. ​ On February 28, 2023, the Company sold FleetNet, a wholly owned subsidiary and reportable operating segment of the Company. Following the sale, FleetNet is reported as discontinued operations. As such, historical results of FleetNet have been excluded from both continuing operations and segment results for all periods presented, and reclassifications have been made to the prior-period financial statements to conform to the current-year presentation. ​ The Company’s reportable operating segments are as follows: ​ ● The Asset-Based segment includes the results of operations of ABF Freight System, Inc. and certain other subsidiaries. The segment operations include national, inter-regional, and regional transportation of general commodities through standard, expedited, and guaranteed LTL services. The Asset-Based segment provides services to the Asset-Light segment, including freight transportation related to managed transportation solutions and other services. ​ As previously discussed in Note A, the Asset-Based segment’s contractual employees are covered under the 2023 ABF NMFA, which was implemented on July 16, 2023, effective retroactive to July 1, 2023, and will remain in effect through June 30, 2028. The major economic provisions of the 2023 ABF NMFA include wage and mileage rate increases in each year of the contract, with the initial increase effective retroactive to July 1, 2023; profit-sharing bonuses upon the Asset-Based segment’s achievement of certain annual operating ratios for any full calendar year under the contract; an additional paid holiday; two additional paid sick days; and a new non-CDL employee classification. The 2023 ABF NMFA and the related supplemental agreements provide for annual contribution rate increases to multiemployer health and welfare and pension funds to which ABF Freight contributed under the previous agreement. ​ ● The Asset-Light segment includes the results of operations of the Company’s service offerings in truckload, ground expedite, dedicated, intermodal, household goods moving, managed transportation, warehousing and distribution, and international freight transportation for air, ocean, and ground. The Asset-Light segment provides services to the Asset-Based segment. ​ The Company’s other business activities and operations that are not reportable segments include ArcBest Corporation (the parent holding company) and certain subsidiaries. Certain costs incurred by the parent holding company and the Company’s shared services subsidiary are allocated to the reporting segments. The Company eliminates intercompany transactions in consolidation. However, the information used by the Company’s management with respect to its reportable operating segments is before intersegment eliminations of revenues and expenses. ​ Shared services represent costs incurred to support all segments, including sales, pricing, customer service, marketing, capacity sourcing functions, human resources, financial services, information technology, and other company-wide services. Certain overhead costs are not attributable to any segment and remain unallocated in “Other and eliminations.” Included in unallocated costs are expenses related to investor relations, legal, the Company’s Board of Directors, and certain technology investments. Shared services costs attributable to the reportable operating segments are predominantly allocated based upon estimated and planned resource utilization-related metrics such as estimated shipment levels or number of personnel supported. The bases for such charges are modified and adjusted by management when necessary or appropriate to reflect fairly and equitably the actual incidence of cost incurred by the reportable operating segments. Management believes the methods used to allocate expenses are reasonable. ​ Further classifications of operations or revenues by geographic location are impracticable and, therefore, are not provided. The Company’s foreign operations are not significant. ​ The following table reflects reportable operating segment information from continuing operations for the years ended December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands) REVENUES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,871,004 ​ $ 3,010,900 ​ $ 2,573,773 ​ Asset-Light ​ 1,680,645 ​ 2,139,272 ​ 1,300,626 ​ Other and eliminations ​ (124,206) ​ (121,164) ​ (108,214) ​ Total consolidated revenues ​ $ 4,427,443 ​ $ 5,029,008 ​ $ 3,766,185 ​ OPERATING EXPENSES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Salaries, wages, and benefits ​ $ 1,379,756 ​ $ 1,293,487 ​ $ 1,198,253 ​ Fuel, supplies, and expenses ​ 361,355 ​ 378,558 ​ 266,139 ​ Operating taxes and licenses ​ 55,918 ​ 52,290 ​ 49,461 ​ Insurance ​ 52,025 ​ 47,382 ​ 37,800 ​ Communications and utilities ​ 19,288 ​ 18,949 ​ 18,773 ​ Depreciation and amortization ​ 104,165 ​ 97,322 ​ 93,799 ​ Rents and purchased transportation ​ 338,575 ​ 441,167 ​ 364,345 ​ Shared services ​ ​ 279,248 ​ ​ 281,698 ​ ​ 263,532 ​ (Gain) loss on sale of property and equipment and lease impairment charges (1) ​ 982 ​ (12,468) ​ (8,676) ​ Innovative technology costs (2) ​ ​ 21,711 ​ ​ 27,207 ​ ​ 27,631 ​ Other ​ 4,829 ​ 4,175 ​ 2,009 ​ Total Asset-Based ​ 2,617,852 ​ 2,629,767 ​ 2,313,066 ​ Asset-Light ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Purchased transportation ​ 1,435,604 ​ 1,784,668 ​ 1,097,332 ​ Supplies and expenses (3) ​ 12,094 ​ 13,955 ​ 8,661 ​ Depreciation and amortization (4) ​ 20,370 ​ 20,730 ​ 11,387 ​ Shared services ​ ​ 194,296 ​ ​ 218,133 ​ ​ 132,137 ​ Contingent consideration (5) ​ ​ (19,100) ​ ​ 18,300 ​ ​ — ​ Lease impairment charges (6) ​ ​ 14,407 ​ ​ — ​ ​ — ​ Legal settlement (7) ​ ​ 9,500 ​ ​ — ​ ​ — ​ Gain on sale of subsidiary (8) ​ ​ — ​ ​ (402) ​ ​ (6,923) ​ Other (3) ​ ​ 25,745 ​ 31,163 ​ 11,635 ​ Total Asset-Light ​ 1,692,916 ​ 2,086,547 ​ 1,254,229 ​ Other and eliminations ​ (55,944) ​ (81,832) ​ (78,088) ​ Total consolidated operating expenses ​ $ 4,254,824 ​ $ 4,634,482 ​ $ 3,489,207 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ OPERATING INCOME (LOSS) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 253,152 ​ $ 381,133 ​ $ 260,707 ​ Asset-Light ​ (12,271) ​ 52,725 ​ 46,397 ​ Other and eliminations (9) ​ (68,262) ​ (39,332) ​ (30,126) ​ Total consolidated operating income ​ $ 172,619 ​ $ 394,526 ​ $ 276,978 ​ OTHER INCOME (COSTS) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest and dividend income ​ $ 14,728 ​ $ 3,873 ​ $ 1,226 ​ Interest and other related financing costs ​ (9,094) ​ (7,726) ​ (8,914) ​ Other, net (10) ​ 8,662 ​ (2,370) ​ 3,797 ​ Total other income (costs) ​ 14,296 ​ (6,223) ​ (3,891) ​ INCOME BEFORE INCOME TAXES ​ $ 186,915 ​ $ 388,303 ​ $ 273,087 ​ (1) For 2023, includes a $0.7 million noncash lease-related impairment charge for an Asset-Based service center. For 2022, includes a $4.3 million noncash gain on a like-kind property exchange of a service center, with the remaining gains related primarily to sales of replaced equipment. For 2021, includes an $8.6 million gain on the sale of unutilized service center property. (2) Represents costs associated with the freight handling pilot test program at ABF Freight, for which the decision was made to pause the pilot during third quarter 2023. (3) For 2022 and 2021, amounts have been adjusted from those previously reported to reclass certain facility rent expense between line items within the Asset-Light segment. Adjustments made are not material. (4) Depreciation and amortization includes amortization of intangibles associated with acquired businesses. (5) Represents the change in fair value of the contingent earnout consideration to the MoLo acquisition (see Note C). (6) Represents noncash lease-related impairment charges for certain Asset-Light office spaces that were made available for sublease. (7) Represents estimated expenses to settle a claim related to the classification of certain Asset-Light employees under the Fair Labor Standards Act . (8) Gain recognized relates to the sale of the labor services portion of the Asset-Light segment’s moving business in second quarter 2021, including the contingent amount recognized in second quarter 2022 when the funds were released from escrow. (9) For 2023, “Other and eliminations” includes $15.1 million of noncash lease-related impairment charges for a freight handling pilot facility. (10) Includes the components of net periodic benefit cost (credit) other than service cost related to the Company’s SBP and postretirement plans (see Note K) and proceeds and changes in cash surrender value of life insurance policies. For 2023, includes a $3.7 million fair value increase related to the Company’s equity investment in Phantom Auto, based on an observable price change during second quarter 2023 (see Note C). ​ ​ The following table reflects information about revenues from customers and intersegment revenues for the years ended December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands) Revenues from customers ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,749,803 ​ $ 2,896,284 ​ $ 2,470,529 ​ Asset-Light ​ 1,673,399 ​ 2,128,394 ​ 1,291,679 ​ Other ​ 4,241 ​ 4,330 ​ 3,977 ​ Total consolidated revenues ​ $ 4,427,443 ​ $ 5,029,008 ​ $ 3,766,185 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Intersegment revenues ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 121,201 ​ $ 114,616 ​ $ 103,244 ​ Asset-Light ​ ​ 7,246 ​ ​ 10,878 ​ ​ 8,947 ​ Other and eliminations ​ ​ (128,447) ​ ​ (125,494) ​ ​ (112,191) ​ Total intersegment revenues ​ $ — ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total segment revenues ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,871,004 ​ ​ 3,010,900 ​ $ 2,573,773 ​ Asset-Light ​ ​ 1,680,645 ​ ​ 2,139,272 ​ ​ 1,300,626 ​ Other and eliminations ​ ​ (124,206) ​ ​ (121,164) ​ ​ (108,214) ​ Total consolidated revenues ​ $ 4,427,443 ​ $ 5,029,008 ​ $ 3,766,185 ​ ​ The following table provides capital expenditure and depreciation and amortization information by reportable operating segment from continuing operations: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ 2023 2022 2021 ​ ​ ​ (in thousands) ​ CAPITAL EXPENDITURES, GROSS ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based (1) ​ $ 207,072 ​ $ 137,117 ​ $ 96,180 ​ Asset-Light ​ ​ 7,587 ​ ​ 14,372 ​ ​ 9,565 ​ Other and eliminations (2)(3) ​ 37,752 ​ 77,720 ​ 11,193 ​ ​ ​ $ 252,411 ​ $ 229,209 ​ $ 116,938 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ ​ 2023 2022 2021 ​ ​ ​ (in thousands) ​ DEPRECIATION AND AMORTIZATION EXPENSE (2) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 104,165 ​ $ 97,322 ​ $ 93,799 ​ Asset-Light (4) ​ ​ 20,370 ​ ​ 20,730 ​ ​ 11,387 ​ Other and eliminations (2) ​ 20,814 ​ 20,107 ​ 17,374 ​ ​ ​ $ 145,349 ​ $ 138,159 ​ $ 122,560 ​ (1) Includes assets acquired through notes payable of $33.5 million, $79.0 million, and $59.7 million in 2023, 2022, and 2021, respectively. (2) Other and eliminations includes certain assets held for the benefit of multiple segments, including information systems equipment. For 2022, also includes the purchase of a property for $37.5 million. Depreciation and amortization associated with these assets is allocated to the reporting segments. Depreciation and amortization expense includes amortization of internally developed capitalized software which has not been included in gross capital expenditures presented in the table. (3) Includes assets acquired through notes payable of $3.4 million in 2022. (4) Includes amortization of intangibles of $12.8 million, $12.9 million, and $5.3 million in 2023, 2022, and 2021, respectively. ​ A table of assets by reportable operating segment has not been presented as segment assets are not included in reports regularly provided to management nor does management consider segment assets for assessing segment operating performance or allocating resources. ​ The Company incurred research and development costs of $52.4 million and $40.8 million for the year ended December 31, 2023 and 2022, respectively, related to innovative technology initiatives. ​ The following table presents operating expenses by category on a consolidated basis: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands) ​ OPERATING EXPENSES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Salaries, wages, and benefits ​ $ 1,781,304 ​ $ 1,728,653 ​ $ 1,527,533 ​ Rents, purchased transportation, and other costs of services ​ 1,642,669 ​ 2,100,663 ​ 1,349,106 ​ Fuel, supplies, and expenses (1) ​ 479,688 ​ 488,009 ​ 360,657 ​ Depreciation and amortization (2) ​ 145,349 ​ 138,159 ​ 122,560 ​ Contingent consideration (3) ​ ​ (19,100) ​ ​ 18,300 ​ ​ — ​ Lease impairment charges (4) ​ ​ 30,162 ​ ​ — ​ ​ — ​ Other (1)(5) ​ 194,752 ​ 160,698 ​ 129,351 ​ ​ ​ $ 4,254,824 ​ $ 4,634,482 ​ $ 3,489,207 ​ (1) For 2022 and 2021, amounts have been adjusted from those previously reported to reclass certain facility rent expense between line items within the Asset-Light segment. Adjustments made are not material. (2) Includes amortization of intangibles assets. (3) Represents the change in fair value of the contingent earnout consideration related to the MoLo acquisition (see Notes C and E). (4) Represents noncash lease-related impairment charges for a freight handling pilot facility, a service center, and office spaces that were made available for sublease. (5) For 2023, includes estimated expenses of $9.5 million to settle a claim related to the classification of certain Asset-Light employees under the Fair Labor Standards Act . For 2022, includes a $12.5 million gain related to the sale of property and equipment within the Asset-Based segment and the sale of replaced equipment and a like-kind exchange of a service center property in the prior year. For 2021, includes a $6.9 million gain related to the sale of a subsidiary within the Asset-Light segment and an $8.6 million gain related to the sale of an unutilized service center property within the Asset-Based segment. For 2023, 2022, and 2021, also includes innovative technology costs of $52.4 million, $40.8 million, and $32.8 million, respectively, associated with the freight handling pilot program at ABF Freight, costs related to the Company’s customer pilot offering of Vaux TM , and initiatives to optimize performance through technological innovation.

LEGAL PROCEEDINGS, ENVIRONMENTA

LEGAL PROCEEDINGS, ENVIRONMENTAL MATTERS, AND OTHER EVENTS	12 Months Ended
	Dec. 31, 2023
LEGAL PROCEEDINGS, ENVIRONMENTAL MATTERS, AND OTHER EVENTS
LEGAL PROCEEDINGS, ENVIRONMENTAL MATTERS, AND OTHER EVENTS	NOTE P – LEGAL PROCEEDINGS, ENVIRONMENTAL MATTERS, AND OTHER EVENTS ​ The Company is involved in various legal actions arising in the ordinary course of business. The Company maintains liability insurance against certain risks arising out of the normal course of its business, subject to certain self-insured retention limits. The Company routinely establishes and reviews the adequacy of reserves for estimated legal, environmental, and self-insurance exposures. While management believes that amounts accrued in the consolidated financial statements are adequate, estimates of these liabilities may change as circumstances develop. Considering amounts recorded, routine legal matters are not expected to have a material adverse effect on the Company’s financial condition, results of operations, or cash flows. ​ Legal Proceedings ​ In January 2023, the Company and MoLo were named as defendants in lawsuits related to an auto accident which involved a MoLo contract carrier. The accident occurred prior to the Company’s acquisition of MoLo on November 1, 2021. The Company intends to vigorously defend against these lawsuits. The Company believes that a loss related to this matter is reasonably possible. The Company cannot estimate the amount or a range of reasonably possible losses for this matter, if any, at this time; however, it is reasonably possible that such amounts could be material to the Company’s financial condition, results of operations, or cash flows. The Company will pursue recovery for its losses, if any, against all available sources, including, but not limited to, insurance and any potentially responsible third parties. ​ Environmental Matters ​ The Company’s subsidiaries store fuel for use in tractors and trucks in underground tanks at certain facilities. Maintenance of such tanks is regulated at the federal and, in most cases, state levels. The Company believes it is in substantial compliance with all such regulations. The Company’s underground storage tanks are required to have leak detection systems. The Company is not aware of any leaks from such tanks that could reasonably be expected to have a material adverse effect on the Company. ​ The Company has received notices from the Environmental Protection Agency (the “EPA”) and others that it has been identified as a potentially responsible party under the Comprehensive Environmental Response Compensation and Liability Act of 1980 , as amended, or other federal or state environmental statutes, at several hazardous waste sites. After investigating the Company’s involvement in waste disposal or waste generation at such sites, the Company has either agreed to de minimis settlements or determined that its obligations, other than those specifically accrued with respect to such sites, would involve immaterial monetary liability, although there can be no assurances in this regard. The Company maintains a reserve within accrued expenses for estimated environmental cleanup costs of properties currently or previously operated by the Company. Amounts accrued reflect management’s best estimate of the future undiscounted exposure related to identified properties based on current environmental regulations, management’s experience with similar environmental matters, and testing performed at certain sites. ​ On March 20, 2023, ABF Freight entered into a consent decree with the EPA (the “Consent Decree”) to resolve alleged compliance issues under the federal Clean Water Act ​ Other Events ​ During second quarter 2023, the Company received a Notice of Assessment from a state regarding an ongoing sales and use tax audit for the trailing time period of December 1, 2018 to March 31, 2021. This notice is in addition to the February 2021 Notice of Assessment from that state pertaining to uncollected sales and use tax, including interest and penalties, for the period of September 1, 2016 to November 30, 2018. The Company does not agree with the basis of these assessments and filed an appeal for the 2023 assessment in October 2023 on the same legal basis as the appeal filed in May 2021 for the earlier assessment. The Company has previously accrued an amount related to these assessments consistent with applicable accounting guidance, but if the state prevails in its position, the Company may owe additional tax. Management does not believe the resolution of this matter will have a material adverse effect on the Company’s financial condition, results of operations, or cash flows. ​ During fourth quarter 2023, the Company tentatively settled a claim related to the classification of certain Asset-Light employees under the Fair Labor Standards Act ​

SCHEDULE II - VALUATION AND QUA

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES	12 Months Ended
	Dec. 31, 2023
SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES
SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES	SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS AND RESERVES ARCBEST CORPORATION ​ On February 28, 2023, the Company sold FleetNet America, Inc. (“FleetNet”), a wholly owned subsidiary and reportable operating segment of the Company. The sale of FleetNet was accounted for as discontinued operations. As such, reclassifications have been made to the balances, additions, and deductions below to exclude the impact of FleetNet. (See Note D to the Company’s consolidated financial statements included in Part II, Item 8 of the Annual Report on Form 10-K). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balances at ​ Additions ​ ​ ​ ​ Balances at ​ ​ ​ Beginning of ​ Charged to Costs ​ Charged to ​ ​ ​ ​ End of ​ Description Period and Expenses Other Accounts Deductions Period ​ ​ (in thousands) Year Ended December 31, 2023 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deducted from asset accounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance for credit losses and revenue adjustments ​ $ 13,892 ​ $ 3,633 ​ $ 3,512 (a) $ 10,691 (b) $ 10,346 ​ Allowance for other accounts receivable ​ $ 713 ​ $ 18 (c) $ — ​ $ — ​ $ 731 ​ Allowance for deferred tax assets ​ $ 1,707 ​ $ — ​ $ — ​ $ (44) (d) $ 1,751 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2022 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deducted from asset accounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance for credit losses and revenue adjustments ​ $ 13,016 ​ $ 6,852 ​ $ 2,761 (a) $ 8,737 (b) $ 13,892 ​ Allowance for other accounts receivable ​ $ 690 ​ $ 23 (c) $ — ​ $ — ​ $ 713 ​ Allowance for deferred tax assets ​ $ 2,196 ​ $ — ​ $ — ​ $ 489 (d) $ 1,707 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deducted from asset accounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance for credit losses and revenue adjustments ​ $ 7,693 ​ $ 1,334 ​ $ 7,783 (a)(e) $ 3,794 (b) $ 13,016 ​ Allowance for other accounts receivable ​ $ 660 ​ $ 30 (c) $ — ​ $ — ​ $ 690 ​ Allowance for deferred tax assets ​ $ 1,284 ​ $ — ​ $ — ​ $ (912) (d) $ 2,196 ​ ​ (a) Change in allowance due to recoveries of amounts previously written off and revenue adjustments. (b) Includes uncollectible accounts written off and revenue adjustments. (c) Charged to workers’ compensation expense. (d) Change in allowance due to changes in expectations of realization of certain federal and state net operating losses and federal and state deferred tax assets. (e) Includes allowance assumed in the acquisition of MoLo Solutions, LLC. (See Note E to the Company’s consolidated financial statements included in Part II, Item 8 of the Annual Report on Form 10-K) .

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2023
ACCOUNTING POLICIES
Consolidation	Consolidation:
Segment Information	Segment Information:
Use of Estimates	Use of Estimates:
Reclassifications	Reclassifications: ​ Certain reclassifications have been made to the prior period presentation of other long-term liabilities to conform to the current-year presentation of the contingent consideration liability on a separate line in the consolidated balance sheets. For the years ended December 31, 2022 and 2021, certain reclassifications have been made between operating expenses lines of the Asset-Light segment to conform to the current-year presentation of certain facility rent expenses. There was no impact on total liabilities or total operating expenses as a result of these reclassifications.
Cash, Cash Equivalents, and Short-Term Investments	​ Cash, Cash Equivalents, and Short-Term Investments: ​ Certificates of deposit are valued at cost plus accrued interest, which approximates fair value. Held-to-maturity U.S. Treasury securities are recorded at amortized cost with interest and amortization of premiums and discounts included in interest income. Quarterly, the Company evaluates held-to-maturity securities for any other-than-temporary impairments related to any intention to sell or requirement to sell before its amortized costs are recovered. If a security is considered to be other-than-temporarily impaired, the difference between amortized cost and the amount that is determined to be recoverable is recorded in operating income.
Concentration of Credit Risk	Concentration of Credit Risk: ​ The Company’s services are provided primarily to customers throughout the United States and, to a lesser extent, Canada, Mexico, and other international locations. On a consolidated basis, the Company had no single customer representing more than 2% of its revenues in 2023, 2022, or 2021 or more than 5% of its accounts receivable balance at December 31, 2023 and 2022. The Company performs ongoing credit evaluations of its customers and generally does not require collateral. Historically, credit losses have been within management’s expectations.
Receivable Allowances	Receivable Allowances: ​
Property, Plant and Equipment, Including Repairs and Maintenance	Property, Plant and Equipment, Including Repairs and Maintenance:
Computer Software for Internal Use, Including Web Site Development and Cloud Computing Costs	Computer Software for Internal Use, Including Web Site Development and Cloud Computing Costs: straight-line method generally over 2 to 7 years. Capitalized costs related to cloud computing and hosting arrangements are presented within prepaid expenses in the accompanying consolidated balance sheets. The amount of costs capitalized within any period is dependent on the nature of software development activities and projects in each period.
Impairment Assessment of Long-Lived Assets	Impairment Assessment of Long-Lived Assets: . ​ Assets to be disposed of are reclassified as assets held for sale at the lower of their carrying amount or fair value less cost to sell. Assets held for sale primarily represent Asset-Based segment nonoperating properties, older revenue equipment, and other equipment. Adjustments to write down assets to fair value less the amount of costs to sell are reported in operating income. Assets held for sale are expected to be disposed of by selling the assets within the next 12 months. Gains and losses on property and equipment are reported in operating income. Assets held for sale of $1.5 million and $0.8 million were reported within other long-term assets as of December 31, 2023 and 2022, respectively.
Business Combinations	Business Combinations: ​
Contingent Consideration	Contingent Consideration: ​
Goodwill and Intangible Assets	Goodwill and Intangible Assets: ​ Indefinite-lived intangible assets are also not amortized but rather are evaluated for impairment annually or more frequently if indicators of impairment exist. Consistent with goodwill, the Company typically assesses qualitative factors but may from time to time perform a quantitative assessment to determine if it is more likely than not that the fair value of indefinite-lived intangible assets is less than its carrying value; if applicable, a quantitative analysis is performed if it is determined it is more likely than not the indefinite-lived intangible is impaired. ​ The Company amortizes finite-lived intangible assets over their respective estimated useful lives. ​
Income Taxes	Income Taxes: ​ Management applies considerable judgment in determining the consolidated income tax provision, including valuation allowances on deferred tax assets. The valuation allowance for deferred tax assets is determined by evaluating whether it is more likely than not that the benefits of deferred tax assets will be realized through future reversal of existing taxable temporary differences, taxable income in carryback years in jurisdictions in which they are allowable, projected future taxable income, or tax-planning strategies. Uncertain tax positions, which also require significant judgment, are measured to determine the amounts to be recognized in the financial statements. The income tax provision and valuation allowances are complicated by complex and frequently changing rules administered in multiple jurisdictions, including U.S. federal, state, and foreign governments.
Long Term Investments	Long-Term Investments:
Book Overdrafts	Book Overdrafts: ​
Insurance Reserves	Insurance Reserves ​ Liabilities for self-insured workers’ compensation and third-party casualty claims are based on the case reserve amounts plus an estimate of loss development and incurred but not reported (“IBNR”) claims, which is developed from an independent actuarial analysis. The process of determining reserve requirements utilizes historical trends and involves an evaluation of claim frequency and severity, claims management, and other factors. Case reserves are evaluated as loss experience develops and new information becomes available. Adjustments to previously estimated aggregate reserves are reflected in financial results in the periods in which they are made. Aggregate reserves represent an estimate of the costs of claims incurred, and it is possible that the ultimate liability may differ significantly from such estimates. ​ The Company develops an estimate of self-insured cargo loss and damage claims liabilities based on historical trends and certain event-specific information. Claims liabilities are recorded in accrued expenses and are not offset by insurance receivables which are reported in other accounts receivable.
Loss Contingencies	Loss Contingencies:
Long-Term Debt	Long-Term Debt:
Interest Rate Swap Derivative Instruments	Interest Rate Swap Derivative Instruments
Leases	Leases: ​ The Company elected the short-term lease exemption for all classes of assets to include real property, revenue equipment, and service, office, and other equipment. The Company adopted the policy election as a lessee for all classes of assets to account for each lease component and its related non-lease component(s) as a single lease component. In determining the discount rate, the Company uses ArcBest Corporation’s incremental borrowing rate unless the rate implicit in the lease is readily determinable when entering into a lease as a lessee. The incremental borrowing rate is determined by the price of a fully collateralized loan with similar terms based on current market rates. ​ An assessment is made on or after the effective date of newly signed contracts as to whether the contract is, or contains, a lease at the inception of a contract. The assessment is based on: (1) whether the contract involves the use of a distinct identified asset; (2) whether the Company obtains the right to substantially all the economic benefit from the use of the asset throughout the period; and (3) whether the Company has the right to direct the use of the asset. The operating right-of-use asset is measured as the initial amount of the operating lease liability, plus any initial direct costs incurred, less any prepayments prior to commencement or lease incentives received. The operating lease liability is initially measured at the present value of the lease payments, discounted using the Company’s secured incremental borrowing rate for the same term as the underlying lease unless the interest rate implicit in the lease is readily determined, then the implicit rate will be used. Lease payments included in the measurement of the lease liability are comprised of the following: (1) the fixed noncancelable lease payments, (2) payments for optional renewal periods where it is reasonably certain the renewal period will be exercised, and (3) payments for early termination options unless it is reasonably certain the lease will not be terminated early. Variable lease payments based on an index or rate are initially measured using the index or rate in effect at lease commencement and included in the measurement of the initial lease liability. Additional payments based on the change in an index or rate are recorded as a period expense when incurred. Lease modifications result in remeasurement of the lease liability. ​
Nonunion Defined Benefit Pension, Supplemental Benefit, and Postretirement Health Benefit Plans	Supplemental Benefit and Postretirement Health Benefit Plans: active service period of the plan participants and amortizing unrecognized prior service credits over the remaining years of service until full eligibility of the active participants at the time of the plan amendment which created the prior service credit. A corridor approach is not used for determining the amounts of net actuarial losses to be amortized. ​ The Company has not incurred service cost under the SBP since the accrual of benefits under the plan was frozen on December 31, 2009, however, the Company incurs service cost under the postretirement health benefit plan which is reported within operating expenses in the consolidated statements of operations. The other components of net periodic benefit cost (credit) of the SBP (including pension settlement expense) and the postretirement health benefit plan are reported within the other line item of other income (costs). ​ The expense and liability related to the postretirement health benefit plan are measured based upon a number of assumptions and using the services of a third-party actuary. Assumptions are made regarding the discount rate, expected retirement age, mortality, employee turnover, and future increases in health care costs. The discount rates used to discount the SBP and postretirement health benefit plan obligations are determined by matching projected cash distributions with appropriate high-quality corporate bond yields in a yield curve analysis. The assumptions used directly impact the net periodic benefit cost (credit) for a particular year. An actuarial gain or loss results when actual experience varies from the assumptions or when there are changes in actuarial assumptions. Actuarial gains and losses are not included in net periodic benefit cost (credit) in the period when they arise but are recognized as a component of other comprehensive income or loss and subsequently amortized as a component of net periodic benefit cost (credit). ​ The Company uses December 31 as the measurement date for the SBP and postretirement health benefit plan. Plan obligations are also remeasured upon curtailment and upon settlement. Benefit distributions under the SBP individually exceed the annual interest cost of the plan, which triggers settlement accounting. The Company records the related settlement expense when the amount of the benefit to be distributed is fixed, which is generally upon an employee’s termination of employment. There was no pension settlement expense incurred for the SBP in 2023, 2022, or 2021.
Revenue Recognition	Revenue Recognition: ​ Asset-Based Segment Asset-Based segment revenues consist primarily of less-than-truckload freight delivery. Performance obligations are satisfied upon final delivery of the freight to the specified destination. Revenue is recognized based on the relative transit time in each reporting period with expenses recognized as incurred. A bill-by-bill analysis is used to establish estimates of revenue in transit for recognition in the appropriate period. Because the bill-by-bill methodology utilizes the approximate location of the shipment in the delivery process to determine the revenue to recognize, management believes it to be a reliable method. ​ Certain contracts may provide for volume-based or other discounts which are accounted for as variable consideration. The Company estimates these amounts based on a historical expectation of discounts to be earned by customers, and revenue is recognized based on the estimates. Management believes that actual amounts will not vary significantly from estimates of variable consideration. ​ Revenue, purchased transportation expense, and third-party service expenses are reported on a gross basis for certain shipments and services where the Company utilizes a third-party carrier for pickup, linehaul, delivery of freight, or performance of services but remains primarily responsible for fulfilling delivery to the customer and maintains discretion in setting the price for the services. ​ Asset-Light Segment Asset-Light segment revenues consist primarily of asset-light logistics services using third-party vendors to provide transportation services. Asset-Light segment revenue is generally recognized based on the relative transit time in each reporting period using estimated standard delivery times for freight in transit at the end of the reporting period. Purchased transportation expense is recognized as incurred consistent with the recognition of revenue. ​ Revenue and purchased transportation expense are reported on a gross basis for shipments and services where the Company utilizes a third-party carrier for pickup and delivery but remains primarily responsible to the customer for delivery and maintains discretion in setting the price for the service. ​ Other Recognition and Disclosure Payment terms with customers may vary depending on the service provided, location or specific agreement with the customer. The term between invoicing and when payment is due is not significant. For certain services, payment is required before the services are provided to the customer. ​ The Company expenses sales commissions when incurred because the amortization period is one year or less. ​ The Company has elected not to disclose the value of unsatisfied performance obligations for contracts with an original length of one year or less or contracts for which revenue is recognized at the amount to which the Company has the right to invoice for services performed. ​
Comprehensive Income or Loss	Comprehensive Income or Loss:
Accelerated Share Repurchase	Accelerated Share Repurchase:
Earnings Per Share	Earnings Per Share: ​
Share-Based Compensation	Share-Based Compensation: ​ Share-based awards are amortized to compensation expense on a straight-line basis over the vesting period of awards or over the period to which the recipient first becomes eligible for retirement, whichever is shorter, with vesting accelerated upon death or disability. The Company recognizes forfeitures as they occur, and the income tax effects of awards are recognized in the statement of operations when awards vest or are settled.
Fair Value Measurements	Fair Value Measurements: ​ ● Level 1 – Quoted prices for identical assets and liabilities in active markets. ● Level 2 – Quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. ● Level 3 – Unobservable inputs (Company’s market assumptions) that are significant to the valuation model. ​
Environmental Matters	Environmental Matters:
Exit or Disposal Activities	Exit or Disposal Activities: ​
Accounting Pronouncements Not Yet Adopted	Accounting Pronouncements Not Yet Adopted ​ Accounting Standards Codification (“ASC”) Topic 280, Segment Reporting Improvements to Reportable Segment Disclosures ​ ASC Topic 740 , Income Taxes, Improvements to Income Tax Disclosures ​

FINANCIAL INSTRUMENTS AND FAI_2

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Dec. 31, 2023
FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS
Schedule components of cash and cash equivalents, short term investments, and restricted funds	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 December 31 ​ ​ 2023 ​ 2022 ​ ​ (in thousands) ​ Cash and cash equivalents ​ ​ ​ ​ ​ ​ ​ Cash deposits (1) ​ $ 168,472 ​ $ 137,247 ​ Variable rate demand notes (1)(2) ​ — ​ 9,285 ​ Money market funds (3) ​ 93,754 ​ 11,732 ​ Total cash and cash equivalents ​ $ 262,226 ​ $ 158,264 ​ ​ ​ ​ ​ ​ ​ ​ ​ Short-term investments ​ ​ ​ ​ ​ ​ ​ Certificates of deposit (1) ​ $ 67,842 ​ $ 88,851 ​ U.S. Treasury securities (4) ​ ​ — ​ ​ 78,811 ​ Total short-term investments ​ $ 67,842 ​ $ 167,662 ​ (1) Recorded at cost plus accrued interest, which approximates fair value. (2) Amounts may be redeemed on a daily basis with the original issuer. (3) Recorded at fair value as determined by quoted market prices (see amounts presented in the table of financial assets and liabilities measured at fair value within this Note). (4) Recorded at amortized cost plus accrued interest, which approximates fair value. U.S. Treasury securities included in short-term investments are held-to-maturity investments with maturity dates of less than one year.
Schedule of fair value and carrying value disclosures of financial instruments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 ​ ​ (in thousands) ​ ​ ​ ​ Carrying ​ Fair ​ Carrying ​ Fair ​ ​ ​ ​ Value ​ Value ​ Value ​ Value ​ Credit Facility (1) ​ $ 50,000 ​ $ 50,000 ​ $ 50,000 ​ $ 50,000 ​ Notes payable (2) ​ 178,938 ​ 177,149 ​ 214,623 ​ 207,778 ​ New England Pension Fund withdrawal liability (3) ​ ​ 19,402 ​ ​ 18,220 ​ ​ 20,100 ​ ​ 18,911 ​ ​ ​ $ 248,340 ​ $ 245,369 ​ $ 284,723 ​ $ 276,689 ​ (1) The revolving credit facility (the “Credit Facility”) carries a variable interest rate based on Secured Overnight Financing Rate (“SOFR”), plus a margin, priced at market for debt instruments having similar terms and collateral requirements (Level 2 of the fair value hierarchy). (2) Fair value of the notes payable was determined using a present value income approach based on quoted interest rates from lending institutions with which the Company would enter into similar transactions (Level 2 of the fair value hierarchy). (3) ABF Freight’s multiemployer pension plan obligation with the New England Teamsters and Trucking Industry Pension Fund (the “New England Pension Fund”) was restructured under a transition agreement effective on August 1, 2018, which resulted in a related withdrawal liability. The fair value of the outstanding withdrawal liability is equal to the present value of the future withdrawal liability payments, discounted at an interest rate of 5.3% at both December 31, 2023 and 2022, determined using the 20-year U.S. Treasury rate plus a spread (Level 2 of the fair value hierarchy). As of December 31, 2023, the outstanding withdrawal liability totaled $19.4 million, of which $0.7 million was recorded in accrued expenses and the remaining portion was recorded in other long-term liabilities. ​
Schedule of financial assets and liabilities measured at fair value on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ ​ ​ ​ ​ Quoted Prices Significant Significant ​ ​ ​ ​ ​ In Active ​ Observable ​ Unobservable ​ ​ ​ ​ ​ ​ Markets ​ Inputs ​ Inputs ​ ​ ​ Total (Level 1) (Level 2) (Level 3) ​ ​ (in thousands) ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (1) ​ $ 93,754 ​ $ 93,754 ​ $ — ​ $ — ​ Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan (2) ​ 4,627 ​ 4,627 ​ — ​ — ​ Interest rate swap (3) ​ ​ 1,710 ​ ​ — ​ ​ 1,710 ​ ​ — ​ ​ ​ $ 100,091 ​ $ 98,381 ​ $ 1,710 ​ $ — ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration (4) ​ ​ 92,900 ​ ​ — ​ ​ — ​ ​ 92,900 ​ ​ ​ $ 92,900 ​ $ — ​ $ — ​ $ 92,900 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ ​ ​ ​ ​ Quoted Prices Significant Significant ​ ​ ​ ​ ​ In Active ​ Observable ​ Unobservable ​ ​ ​ ​ ​ ​ Markets ​ Inputs ​ Inputs ​ ​ ​ Total (Level 1) (Level 2) (Level 3) ​ ​ (in thousands) ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds (1) ​ $ 11,732 ​ $ 11,732 ​ $ — ​ $ — ​ Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan (2) ​ 3,982 ​ 3,982 ​ — ​ — ​ Interest rate swap (3) ​ ​ 3,526 ​ ​ — ​ ​ 3,526 ​ ​ — ​ ​ ​ $ 19,240 ​ $ 15,714 ​ $ 3,526 ​ $ — ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration (4) ​ ​ 112,000 ​ ​ — ​ ​ — ​ ​ 112,000 ​ ​ ​ $ 112,000 ​ $ — ​ $ — ​ $ 112,000 ​ ​ ​ (1) Included in cash and cash equivalents. (2) Nonqualified deferred compensation plan investments consist of U.S. and international equity mutual funds, government and corporate bond mutual funds, and money market funds which are held in a trust with a third-party brokerage firm. Included in other long-term assets, with a corresponding liability reported within other long-term liabilities. (3) Included in other long-term assets. The fair value of the interest rate swap was determined by discounting future cash flows and receipts based on expected interest rates observed in market interest rate curves adjusted for estimated credit valuation considerations reflecting nonperformance risk of the Company and the counterparty, which are generally considered to be in Level 3 of the fair value hierarchy. However, the Company assessed Level 3 inputs as insignificant to the valuation at December 31, 2023 and 2022 and considers the interest rate swap valuation in Level 2 of the fair value hierarchy. (4) Included as a long-term liability, based on the December 31, 2023 remeasurement as the 2023 target was not achieved. As part of the Agreement and Plan of Merger (the “Merger Agreement”) of MoLo, executed on November 1, 2021, certain additional cash consideration is required to be paid by the Company based on the achievement of certain incremental targets of adjusted EBITDA for each of the years ended December 31, 2023, 2024, and 2025 (see Note E). The estimated fair value of contingent consideration is determined by assessing Level 3 inputs. The Level 3 assessments utilize a Monte Carlo simulation with inputs including scenarios of estimated revenues and adjusted EBITDA to be achieved for the applicable performance periods, volatility factors applied to the simulations, and the discount rate applied, which was 13.3% and 14.0% as of December 2023 and 2022, respectively. Changes in the significant unobservable inputs might result in a significantly higher or lower fair value at the reporting date. The decrease in fair value of contingent earnout consideration as of December 31, 2023, compared to December 31, 2022, reflects revised assumptions for business growth in 2024 and 2025, as well as the impact of softer market conditions during 2023, despite a lower discount rate at the December 31, 2023 remeasurement date.
Schedule of changes in fair value of liabilities measured at fair value using inputs categorized in Level 3	​ ​ ​ ​ ​ ​ ​ ​ Contingent Consideration ​ ​ ​ (in thousands) ​ Balance at December 31, 2022 ​ $ 112,000 ​ Change in fair value included in operating income ​ ​ (19,100) ​ Balance at December 31, 2023 ​ $ 92,900 ​
Schedule of assets measured at fair value on a nonrecurring basis	The following table provides the change in fair value of equity investments on a nonrecurring basis using inputs categorized in Level 3 of the fair value hierarchy: ​ ​ ​ ​ ​ ​ ​ ​ Equity Investment (1) ​ ​ (in thousands) ​ Balance at December 31, 2022 ​ $ 25,000 ​ Change in fair value included in operating income ​ ​ 3,739 ​ Balance at December 31, 2023 ​ $ 28,739 ​ (1) Represents the Company’s equity investment in Phantom Auto, a provider of human-centered remote operation software. The equity investment is accounted for as a nonmarketable equity security without a readily determinable value using the measurement alternative, which allows for the investment to be recorded at cost, less any impairment and adjusted for observable price changes in orderly transactions for an identical or similar equity security of the same issuer. The $3.7 million increase in fair value of the Company’s equity investment was measured as of April 26, 2023, based on an observable price change upon the closing of Phantom Auto’s Series B-2 funding round. The fair value of the investment was estimated using a hybrid method of the Black-Scholes option pricing model and the probability-weighted expected return method. This method produces a per-share value based on a probability-weighted scenario analysis. The scenarios reflect changes to the liquidation preferences based on the potential liquidity event. The Black-Scholes option pricing model used various inputs, including expected volatility, expected term to liquidity, risk-free rate over the expected term, breakpoints values, and liquidation preferences. ​ The following table provides the changes in the long-lived assets measured on a nonrecurring basis for which impairment charges were recognized during the year ended December 31, 2023. The fair value measurements used inputs categorized in Level 3 of the fair value hierarchy. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Lease ​ ​ ​ ​ ​ Carrying Value Impairment Charges (1) Fair Value ​ ​ (in thousands) ​ Operating right-of-use assets ​ $ 48,417 ​ $ (28,124) ​ $ 20,293 ​ Leasehold improvements ​ ​ 3,874 ​ ​ (2,038) ​ ​ 1,836 ​ ​ ​ $ 52,291 ​ $ (30,162) ​ $ 22,129 ​ (1) During the third quarter of 2023, the Company recorded impairment charges of $30.2 million related to operating right-of-use assets and leasehold improvements associated with a freight handling pilot facility, a service center, and office spaces that were made available for sublease. The fair value of these asset groups was estimated at September 1, 2023, using a discounted cash flow method utilizing market-participant discount rates ranging from 7.5% to 9.5% and certain unobservable inputs, including estimated cash flows based on anticipated future sublease terms as determined using third-party real estate broker quotes. See Note H for additional discussion related to these impairment charges.

DISCONTINUED OPERATIONS (Tables

DISCONTINUED OPERATIONS (Tables)	12 Months Ended
	Dec. 31, 2023
FleetNet | Discontinued Operations, Disposed of by Sale
Discontinued Operations
Schedules of Discontinued Operations - Financial information, Assets and liabilities and Cash flows	The following table summarizes the financial results from discontinued operations: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31 ​ ​ 2023 ​ 2022 ​ 2021 ​ ​ (in thousands) Revenues ​ $ 55,929 ​ $ 295,043 ​ $ 213,882 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating expenses ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain on sale of business (1) ​ ​ (70,201) ​ ​ — ​ ​ — Other ​ ​ 54,623 ​ ​ 290,300 ​ ​ 209,874 ​ ​ ​ (15,578) ​ ​ 290,300 ​ ​ 209,874 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating income ​ ​ 71,507 ​ ​ 4,743 ​ ​ 4,008 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other income, net (2) ​ ​ 17 ​ ​ 109 ​ ​ 59 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income from discontinued operations before income taxes ​ ​ 71,524 ​ ​ 4,852 ​ ​ 4,067 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax provision ​ ​ 18,255 ​ ​ 1,291 ​ ​ 1,005 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income from discontinued operations, net of tax ​ $ 53,269 ​ $ 3,561 ​ $ 3,062 (1) The gain recognized during the year ended December 31, 2023 includes post-closing adjustments, including the resolution of certain post-close contingencies in the second quarter of 2023. The total pre-tax gain of $70.2 million includes transaction costs of $3.8 million consisting of consulting fees, professional fees, and employee-related expenses. (2) Includes interest income, net of interest expense, of which the amounts are immaterial for all periods presented. ​ The following table summarizes the assets and liabilities from discontinued operations: ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ ​ (in thousands) ​ Cash and cash equivalents ​ $ 108 ​ Accounts receivable, net ​ ​ 63,022 ​ Other current assets ​ ​ 1,606 ​ Total current assets of discontinued operations ​ $ 64,736 ​ ​ ​ ​ ​ ​ Property, plant and equipment, net ​ ​ 10,350 ​ Goodwill ​ ​ 630 ​ Intangible assets, net ​ ​ 63 ​ Other long-term assets ​ ​ 54 ​ Total long-term assets of discontinued operations ​ $ 11,097 ​ ​ ​ ​ ​ ​ Accounts payable ​ ​ 47,687 ​ Income taxes payable ​ ​ 613 ​ Accrued expenses ​ ​ 3,365 ​ Total current liabilities of discontinued operations ​ $ 51,665 ​ ​ ​ ​ ​ ​ Deferred tax liability ​ ​ 781 ​ Total long-term liabilities of discontinued operations ​ $ 781 ​ ​ Cash flows from discontinued operations of FleetNet were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended ​ ​ December 31 ​ 2023 2022 ​ ​ (in thousands) Net cash provided by operating activities (1) ​ $ 762 ​ $ 2,825 ​ Net cash used in investing activities (2) ​ ​ (397) ​ ​ (3,329) ​ Net cash provided by (used in) financing activities ​ ​ (473) ​ ​ 560 ​ Net increase (decrease) in cash and cash equivalents ​ $ (108) ​ $ 56 ​ (1) Includes depreciation and amortization expense of $0.4 million and $1.9 million for the years ended December 31, 2023 and 2022, respectively. Also includes share-based compensation expense for the year ended December 31, 2023 of $0.3 million, which is included in the “Pre-tax gain on sale of discontinued operations” line of the consolidated statements of cash flows. (2) Includes purchases of property, plant and equipment of $0.1 million and $1.4 million for the years ended December 31, 2023 and 2022, respectively. Excludes the proceeds from the sale of discontinued operations, which are included in cash flows from continuing operations. ​

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2023
GOODWILL AND INTANGIBLE ASSETS
Schedule of goodwill by reportable operating segment	​ ​ ​ ​ ​ ​ ​ Goodwill ​ ​ (in thousands) ​ Balances at December 31, 2021 ​ $ 299,708 ​ Purchase accounting adjustments (1) ​ 5,045 ​ Balances at December 31, 2023 and 2022 ​ $ 304,753 ​ ​ ​ ​ ​ ​ Accumulated impairment at December 31, 2023 and 2022 ​ $ (20,000) ​ (1) Measurement period purchase accounting adjustments represent adjustments to the acquired balance of working capital and goodwill related to the November 1, 2021 acquisition of MoLo.
Schedule of intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ December 31, 2022 ​ ​ Weighted-Average ​ ​ ​ ​ Accumulated ​ Net ​ ​ ​ ​ Accumulated ​ Net ​ Amortization Period Cost Amortization Value ​ Cost Amortization Value ​ ​ (in years) ​ (in thousands) ​ (in thousands) Finite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Customer relationships 12 ​ $ 99,579 ​ $ 51,357 ​ $ 48,222 ​ $ 99,579 ​ $ 42,933 ​ $ 56,646 ​ Other ​ 8 ​ ​ 30,151 ​ ​ 9,523 ​ ​ 20,628 ​ ​ 29,914 ​ ​ 5,127 ​ ​ 24,787 ​ ​ 11 ​ 129,730 ​ 60,880 ​ 68,850 ​ ​ 129,493 ​ 48,060 ​ 81,433 ​ Indefinite-lived intangible asset ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trade name N/A ​ 32,300 ​ N/A ​ 32,300 ​ ​ 32,300 ​ N/A ​ 32,300 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total intangible assets N/A ​ $ 162,030 ​ $ 60,880 ​ $ 101,150 ​ $ 161,793 ​ $ 48,060 ​ $ 113,733 ​
Schedule of future amortization for intangible assets	​ ​ ​ ​ ​ ​ ​ Amortization of ​ ​ Intangible Assets ​ ​ (in thousands) ​ 2024 ​ $ 12,790 ​ 2025 ​ 12,790 ​ 2026 ​ 8,683 ​ 2027 ​ 7,258 ​ 2028 ​ ​ 7,259 ​ Thereafter ​ ​ 20,070 ​ Total amortization ​ $ 68,850 ​ ​

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2023
INCOME TAXES
Schedule of significant components of the provision or benefit for income taxes	Significant components of the provision or benefit for income taxes for the years ended December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands) Current provision on continuing operations: ​ ​ ​ ​ Federal ​ $ 38,860 ​ $ 79,477 ​ $ 55,684 ​ State ​ 10,949 ​ 19,713 ​ 14,229 ​ Foreign ​ 508 ​ 869 ​ 341 ​ ​ ​ 50,317 ​ 100,059 ​ 70,254 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred benefit on continuing operations: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ (4,882) ​ (5,591) ​ (6,119) ​ State ​ (682) ​ (793) ​ (1,570) ​ Foreign ​ (2) ​ (20) ​ 63 ​ ​ ​ (5,566) ​ (6,404) ​ (7,626) ​ Total provision for income taxes on continuing operations ​ $ 44,751 ​ $ 93,655 ​ $ 62,628 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current provision on discontinued operations: ​ ​ ​ ​ Federal ​ $ 14,656 ​ $ 901 ​ $ 767 ​ State ​ 3,599 ​ 236 ​ 201 ​ ​ ​ 18,255 ​ 1,137 ​ 968 ​ Deferred provision on discontinued operations: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ — ​ 114 ​ 21 ​ State ​ — ​ 40 ​ 16 ​ ​ ​ — ​ 154 ​ 37 ​ Total provision for income taxes on discontinued operations ​ $ 18,255 ​ $ 1,291 ​ $ 1,005 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total provision for income taxes ​ $ 63,006 ​ $ 94,946 ​ $ 63,633 ​
Schedule of components of the deferred tax benefit on continuing operations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 ​ 2022 ​ 2021 ​ ​ (in thousands) Amortization, depreciation, and basis differences for property, plant and equipment and other long-lived assets (1) $ 1,744 $ 4,274 $ 1,409 ​ Amortization of intangibles ​ 6,127 ​ (2,995) ​ (555) ​ Changes in reserves for workers’ compensation, third-party casualty, and cargo claims ​ (4,975) ​ (3,713) ​ (3,296) ​ Revenue recognition ​ (50) ​ 6 ​ (1,434) ​ Allowance for credit losses ​ 1,094 ​ (388) ​ 170 ​ Nonunion pension and other retirement plans ​ (3) ​ (4) ​ (3) ​ Multiemployer pension fund withdrawal ​ ​ 180 ​ ​ 172 ​ ​ 164 ​ Federal and state net operating loss carryforwards utilized (generated) ​ (758) ​ 899 ​ (300) ​ State depreciation adjustments ​ (456) ​ (915) ​ 598 ​ Share-based compensation ​ 531 ​ 737 ​ (949) ​ Valuation allowance increase (decrease) ​ 44 ​ (489) ​ 912 ​ Other accrued expenses ​ (2,143) ​ (3,069) ​ (4,056) ​ Prepaid expenses ​ ​ 313 ​ ​ (18) ​ ​ (788) ​ Operating lease right-of-use assets/liabilities – net ​ ​ (8,065) ​ ​ (651) ​ ​ (228) ​ Other ​ 851 ​ (250) ​ 730 ​ Deferred tax benefit ​ $ (5,566) ​ $ (6,404) ​ $ (7,626) ​ (1) The Tax Cuts and Jobs Act , enacted in December 2017, allowed first year bonus depreciation at 100% for assets placed into service between September 27, 2017 and January 1, 2023. Due to an increase in the purchase of assets eligible for 100% depreciation, the deferred tax expense related to the tax depreciation expense in excess of book depreciation increased in 2022, compared to 2021. ​
Schedule of significant components of deferred tax assets and liabilities of continuing operations	Significant components of the deferred tax assets and liabilities of continuing operations at December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 ​ 2022 ​ ​ (in thousands) Deferred tax assets: ​ ​ ​ Accrued expenses ​ $ 60,842 ​ $ 53,785 ​ Operating lease right-of-use liabilities ​ ​ 53,589 ​ ​ 46,056 ​ Supplemental pension liabilities ​ ​ 85 ​ ​ 81 ​ Multiemployer pension fund withdrawal ​ ​ 4,871 ​ ​ 5,063 ​ Postretirement liabilities other than pensions ​ 3,389 ​ 3,137 ​ Share-based compensation ​ 5,249 ​ 5,622 ​ Federal and state net operating loss carryovers ​ 1,511 ​ 753 ​ Receivable allowances ​ ​ 1,951 ​ ​ 2,967 ​ Other ​ 709 ​ 417 ​ Total deferred tax assets ​ 132,196 ​ 117,881 ​ Valuation allowance ​ (1,751) ​ (1,707) ​ Total deferred tax assets, net of valuation allowance ​ 130,445 ​ 116,174 ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ ​ Amortization, depreciation, and basis differences for property, plant and equipment, and other long-lived assets ​ 118,211 ​ 116,290 ​ Operating lease right-of-use assets ​ ​ 43,938 ​ ​ 44,170 ​ Intangibles ​ 10,256 ​ 4,442 ​ Prepaid expenses ​ 5,685 ​ 5,424 ​ Total deferred tax liabilities ​ 178,090 ​ 170,326 ​ Net deferred tax liabilities ​ $ (47,645) ​ $ (54,152) ​ ​
Reconciliation between the effective income tax rate, as computed on income from continuing operations before income taxes, and the statutory federal income tax rate	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 ​ 2022 ​ 2021 ​ ​ (in thousands, except percentages) Income tax provision at the statutory federal rate of 21.0% $ 39,252 $ 81,544 $ 57,348 ​ Federal income tax effects of: ​ ​ ​ ​ ​ ​ ​ ​ ​ State income taxes ​ (2,156) ​ (3,973) ​ (2,658) ​ Nondeductible expenses ​ 4,040 ​ 5,606 ​ 3,596 ​ Life insurance proceeds and changes in cash surrender value ​ (962) ​ 575 ​ (866) ​ Alternative fuel credit ​ (1,302) ​ (2,449) ​ — ​ Net increase (decrease) in valuation allowances ​ 44 ​ (464) ​ 887 ​ Net increase in uncertain tax positions ​ ​ — ​ ​ — ​ ​ 854 ​ Settlement of share-based compensation ​ ​ (3,989) ​ ​ (6,693) ​ ​ (6,021) ​ Foreign tax credits generated ​ ​ (506) ​ ​ (849) ​ ​ (404) ​ Federal research and development tax credits ​ ​ (75) ​ ​ 278 ​ ​ (2,044) ​ Other ​ (368) ​ 311 ​ (1,127) ​ Federal income tax provision ​ 33,978 ​ 73,886 ​ 49,565 ​ State income tax provision ​ 10,267 ​ 18,920 ​ 12,659 ​ Foreign income tax provision ​ 506 ​ 849 ​ 404 ​ Total provision for income taxes ​ $ 44,751 ​ $ 93,655 ​ $ 62,628 ​ Effective tax rate ​ 23.9 % 24.1 % 22.9 %

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2023
LEASES
Schedule of components of lease expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31 ​ 2023 2022 2021 ​ ​ (in thousands) Operating lease expense ​ $ 38,794 ​ $ 31,790 ​ $ 26,552 Variable lease expense ​ ​ 6,804 ​ ​ 4,188 ​ ​ 4,128 Sublease income ​ ​ (246) ​ ​ (391) ​ ​ (626) Total operating lease expense (1) ​ $ 45,352 ​ $ 35,587 ​ $ 30,054 (1) Operating lease expense excludes short-term leases with a term of 12 months or less.
Schedule of operating cash flows from operating lease activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31 ​ ​ 2023 2022 2021 ​ ​ (in thousands) ​ Noncash change in operating right-of-use assets ​ $ 33,470 ​ $ 27,465 ​ $ 24,023 ​ Change in operating lease liabilities ​ ​ (30,550) ​ ​ (24,513) ​ ​ (23,400) ​ Operating right-of-use-assets and lease liabilities, net ​ $ 2,920 ​ $ 2,952 ​ $ 623 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid for amounts included in the measurement of operating lease liabilities ​ $ (35,759) ​ $ (28,830) ​ $ (25,909) ​
Schedule of supplemental balance sheet information related to lease liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ ​ (in thousands, except lease term and discount rate) ​ ​ ​ ​ ​ Land and ​ Equipment ​ ​ ​ Total ​ Structures ​ and Others Operating right-of-use assets (long-term) ​ $ 169,999 ​ $ 169,663 ​ $ 336 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease liabilities (current) ​ $ 32,172 ​ $ 31,865 ​ $ 307 Operating lease liabilities (long-term) ​ 176,621 ​ ​ 176,598 ​ ​ 23 Total operating lease liabilities ​ $ 208,793 ​ $ 208,463 ​ $ 330 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term (in years) ​ ​ 7.4 ​ ​ ​ ​ ​ ​ Weighted-average discount rate ​ ​ 4.29% ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ (in thousands, except lease term and discount rate) ​ ​ ​ ​ ​ ​ Land and ​ Equipment ​ ​ ​ ​ Total ​ Structures ​ and Others ​ Operating right-of-use assets (long-term) ​ $ 166,515 ​ $ 165,822 ​ $ 693 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease liabilities (current) ​ $ 26,225 ​ $ 25,824 ​ $ 401 ​ Operating lease liabilities (long-term) ​ 147,828 ​ ​ 147,534 ​ ​ 294 ​ Total operating lease liabilities ​ $ 174,053 ​ $ 173,358 ​ $ 695 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term (in years) ​ ​ 7.6 ​ ​ ​ ​ ​ ​ ​ Weighted-average discount rate ​ ​ 3.58% ​ ​ ​ ​ ​ ​ ​
Schedule of maturities of operating lease liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equipment ​ ​ ​ ​ ​ ​ Land and ​ and ​ ​ Total Structures (1) Other ​ (in thousands) ​ 2024 ​ $ 40,218 ​ $ 39,905 ​ $ 313 ​ 2025 ​ 36,458 ​ 36,435 ​ 23 ​ 2026 ​ 33,187 ​ 33,187 ​ — ​ 2027 ​ 27,071 ​ 27,071 ​ — ​ 2028 ​ 24,033 ​ 24,033 ​ — ​ Thereafter ​ 86,011 ​ 86,011 ​ — ​ Total lease payments ​ ​ 246,978 ​ ​ 246,642 ​ ​ 336 ​ Less imputed interest ​ ​ (38,185) ​ ​ (38,179) ​ ​ (6) ​ Total ​ $ 208,793 ​ $ 208,463 ​ $ 330 ​ ​ (1) Excludes future minimum lease payments for leases which were executed but had not yet commenced as of December 31, 2023, of $28.8 million which will be paid over approximately 10 years .

LONG-TERM DEBT AND FINANCING _2

LONG-TERM DEBT AND FINANCING ARRANGEMENTS (Tables)	12 Months Ended
	Dec. 31, 2023
LONG-TERM DEBT AND FINANCING ARRANGEMENTS
Schedule of long-term debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 ​ December 31 ​ ​ 2023 2022 ​ ​ (in thousands) ​ Credit Facility (interest rate of 6.6% (1) ​ $ 50,000 ​ $ 50,000 ​ Notes payable (weighted-average interest rate of 3.8% at December 31, 2023) ​ 178,938 ​ 214,623 ​ ​ ​ 228,938 ​ 264,623 ​ Less current portion ​ 66,948 ​ 66,252 ​ Long-term debt, less current portion ​ $ 161,990 ​ $ 198,371 ​ (1) The interest rate swap mitigates interest rate risk by effectively converting the $50.0 million of borrowings under the Credit Facility from variable-rate interest to fixed-rate interest with a per annum rate of 1.55% based on the margin of the Credit Facility as of December 31, 2023 and 2022, respectively.
Scheduled maturities of long-term debt obligations	Scheduled maturities of long term debt obligations as of December 31, 2023 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Credit Notes ​ ​ ​ Total ​ Facility (1) ​ Payable ​ ​ ​ (in thousands) ​ 2024 ​ $ 75,800 ​ $ 3,021 ​ $ 72,779 ​ 2025 ​ 53,388 ​ 2,353 ​ ​ 51,035 ​ 2026 ​ 41,476 ​ 2,211 ​ ​ 39,265 ​ 2027 ​ 74,972 ​ 51,688 ​ ​ 23,284 ​ 2028 ​ 5,520 ​ ​ — ​ ​ 5,520 ​ Total payments ​ 251,156 ​ 59,273 ​ ​ 191,883 ​ Less amounts representing interest ​ 22,218 ​ 9,273 ​ 12,945 ​ Long-term debt ​ $ 228,938 ​ $ 50,000 ​ $ 178,938 ​ (1) The future interest payments included in the scheduled maturities due are calculated using variable interest rates based on the SOFR swap curve, plus the anticipated applicable margin, exclusive of payments on the interest rate swap. ​ ​
Schedule of assets securing notes payable	Assets securing notes payable at December 31 were included in property, plant and equipment as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 ​ ​ (in thousands) Revenue equipment $ 300,922 $ 294,700 ​ Service, office, and other equipment ​ ​ 38,138 ​ ​ 41,522 ​ Total assets securing notes payable ​ 339,060 ​ 336,222 ​ Less accumulated depreciation (1) ​ 135,305 ​ 119,244 ​ Net assets securing notes payable ​ $ 203,755 ​ $ 216,978 ​ (1) Depreciation of assets securing notes payable is included in depreciation expense .

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	12 Months Ended
	Dec. 31, 2023
ACCRUED EXPENSES.
Schedule of accrued expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 ​ ​ 2023 2022 ​ ​ ​ (in thousands) ​ Workers’ compensation, third-party casualty, and loss and damage claims reserves ​ $ 189,948 ​ $ 133,122 ​ Accrued vacation pay ​ 63,183 ​ 58,875 ​ Accrued compensation, including retirement benefits ​ ​ 87,851 ​ ​ 119,836 ​ Taxes other than income ​ 10,743 ​ 11,375 ​ Other ​ 26,304 ​ 15,249 ​ Total accrued expenses ​ $ 378,029 ​ $ 338,457 ​ ​

EMPLOYEE BENEFIT PLANS (Tables)

EMPLOYEE BENEFIT PLANS (Tables)	12 Months Ended
	Dec. 31, 2023
POSTRETIREMENT BENEFIT PLANS
Schedule of changes in benefit obligations and plan assets and disclosure of funded status and accumulated benefit obligation of nonunion defined benefit plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2023 2022 2023 2022 ​ ​ (in thousands) Change in benefit obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Benefit obligations, beginning of year ​ $ 338 ​ $ 381 ​ $ 12,534 ​ $ 16,992 ​ Service cost ​ — ​ — ​ 78 ​ 156 ​ Interest cost ​ 16 ​ 7 ​ 599 ​ 441 ​ Actuarial (gain) loss (1) ​ 4 ​ (50) ​ 1,137 ​ (4,392) ​ Benefits paid ​ — ​ — ​ (680) ​ (663) ​ Benefit obligations, end of year ​ 358 ​ 338 ​ 13,668 ​ 12,534 ​ Change in plan assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value of plan asset, beginning of year ​ — ​ — ​ — ​ — ​ Employer contributions ​ — ​ — ​ 680 ​ 663 ​ Benefits paid ​ — ​ — ​ (680) ​ (663) ​ Fair value of plan assets, end of year ​ — ​ — ​ — ​ — ​ Funded status at period end ​ $ (358) ​ $ (338) ​ $ (13,668) ​ $ (12,534) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated benefit obligation ​ $ 358 ​ $ 338 ​ $ 13,668 ​ $ 12,534 ​ (1) The actuarial losses on the SBP and postretirement health benefit plan for 2023 were primarily related to decreases in the discount rates used to remeasure the plans’ obligations at December 31, 2023 versus the prior year, and the actuarial gains for 2022 were primarily related to increases in the discount rates used in the remeasurement at December 31, 2022. ​
Schedule of amounts recognized in the consolidated balance sheets related to nonunion defined benefit plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2023 2022 2023 2022 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current portion of pension and postretirement liabilities ​ $ — ​ $ — ​ $ (707) ​ $ (676) ​ Pension and postretirement liabilities, less current portion ​ (358) ​ (338) ​ (12,961) ​ (11,858) ​ Liabilities recognized ​ $ (358) ​ $ (338) ​ $ (13,668) ​ $ (12,534) ​ ​
Summary of the components of net periodic benefit cost (credit)	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ ​ Benefit Plan ​ Health Benefit Plan ​ ​ 2023 2022 2021 2023 2022 2021 ​ ​ (in thousands) ​ Service cost ​ $ — ​ $ — ​ $ — ​ $ 78 ​ $ 156 ​ $ 192 ​ Interest cost ​ 16 ​ 7 ​ 4 ​ 599 ​ 441 ​ 427 ​ Amortization of net actuarial (gain) loss (1) ​ (4) ​ 8 ​ 9 ​ (1,326) ​ (765) ​ (548) ​ Net periodic benefit cost (credit) ​ $ 12 ​ $ 15 ​ $ 13 ​ $ (649) ​ $ (168) ​ $ 71 ​ (1) The Company amortizes actuarial gains and losses over the average remaining active service period of the plan participants and does not use a corridor approach. ​
Pre-tax amounts included in accumulated other comprehensive loss that have not yet been recognized in net periodic benefit cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2023 2022 2023 2022 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net actuarial gain ​ $ (9) ​ $ (18) ​ $ (6,806) ​ $ (9,269) ​ ​
Weighted-average assumptions used to determine benefit obligations and net periodic benefit cost for nonunion defined benefit plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2023 2022 2023 2022 Discount rate ​ 4.3 % 4.6 % 4.8 % 5.0 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2023 2022 2021 2023 2022 2021 Discount rate ​ 4.6 % 1.8 % 1.1 % 5.0 % 2.7 % 2.3 % ​
Schedule of the assumed health care cost trend rates for the postretirement health benefit plan	​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 Health care cost trend rate assumed for next year (1) ​ 7.0 % 7.0 % Rate to which the cost trend rate is assumed to decline ​ 4.5 % 4.5 % Year that the rate reaches the cost trend assumed rate 2035 2034 (1) At each December 31 measurement date, health care cost rates for the following year are based on known premiums for the fully insured postretirement health benefit plan. Therefore, the first year of assumed health care cost trend rates presented as of December 31, 2023 and 2022 are for 2025 and 2024, respectively.
Schedule of estimated future benefit payments for nonunion defined benefit plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental Postretirement ​ ​ Benefit ​ Health ​ ​ Plan ​ Benefit Plan ​ ​ ​ ​ ​ ​ ​ 2024 ​ $ — ​ $ 707 ​ 2025 ​ $ — ​ $ 744 ​ 2026 ​ $ — ​ $ 747 ​ 2027 ​ $ — ​ $ 754 ​ 2028 ​ $ 424 ​ $ 761 ​ 2029-2033 ​ $ — ​ $ 3,836 ​ ​
Schedule of multiemployer pension funds and key participation information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension ​ FIP/RP ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Protection Act ​ Status ​ Contributions (d) ​ ​ ​ ​ EIN/Pension ​ Zone Status (b) ​ Pending/ ​ (in thousands) ​ Surcharge Legal Name of Plan Plan Number (a) 2023 2022 Implemented (c) 2023 2022 2021 Imposed (e) Central States, Southeast and Southwest Areas Pension Plan (1)(2) 36-6044243 Critical Critical and Declining Implemented (3) ​ $ 77,708 ​ $ 75,306 ​ $ 71,045 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Western Conference of Teamsters Pension Plan (4) 91-6145047 Green Green No ​ 29,540 ​ 28,051 ​ 25,861 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Central Pennsylvania Teamsters Defined Benefit Plan (1)(4) 23-6262789 Green Green No ​ 15,540 ​ 14,421 ​ 13,931 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ I. B. of T. Union Local No. 710 Pension Fund (5)(6) 36-2377656 Green (7) Green (7) No ​ 10,676 ​ 9,838 ​ 9,553 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ New England Teamsters Pension Fund (8)(9) 04-6372430 Critical and Declining (10) Critical and Declining (10) Implemented (11) ​ 4,636 ​ 4,449 ​ 4,357 ​ No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ All other plans in the aggregate ​ ​ ​ ​ ​ ​ ​ ​ ​ 24,384 ​ 22,493 ​ 22,146 ​ ​ Total multiemployer pension contributions paid (12) ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 162,484 ​ $ 154,558 ​ $ 146,893 ​ ​ Table Heading Definitions ​ (a) The “EIN/Pension Plan Number” column provides the Federal Employer Identification Number (“EIN”) and the three-digit plan number, if applicable. (b) Unless otherwise noted, the most recent PPA zone status available in 2023 and 2022 is for the plan’s year-end status at December 31, 2022 and 2021, respectively, and prior to financial assistance from the Pension Relief Act. The zone status is based on information received from the plan and was certified by the plan’s actuary. Green zone funds are those that are in neither endangered, critical, or critical and declining status and generally have a funded percentage of at least 80% . (c) The “FIP/RP Status Pending/Implemented” column indicates if a funding improvement plan (“FIP”) or a rehabilitation plan (“RP”), if applicable, is pending or has been implemented. (d) Amounts reflect contributions made in the respective year and differ from amounts expensed during the year. (e) The surcharge column indicates if a surcharge was paid by ABF Freight to the plan. ​ Table Footnotes ​ (1) ABF Freight System, Inc. was listed by the plan as providing more than 5% of the total contributions to the plan for the plan years ended December 31, 2022 and 2021. (2) Information for this fund was obtained from the 2022 annual funding notice, other notices received from the plan such as the 2023 notice of critical status, and the Form 5500 filed for the plan years ended December 31, 2022 and 2021. (3) Adopted a rehabilitation plan effective March 25, 2008 as updated. Utilized amortization extension granted by the IRS effective December 31, 2003. (4) Information for this fund was obtained from the annual funding notice, other notices received from the plan, and the Form 5500 filed for the plan years ended December 31, 2022 and 2021. (5) The Company was listed by the plan as providing more than 5% of the total contributions to the plan for the plan year ended January 31, 2023. (6) Information for this fund was obtained from the annual funding notice, other notices received from the plan, and the Form 5500 filed for the plan years ended January 31, 2023 and 2022. (7) PPA zone status relates to plan years February 1, 2022 – January 31, 2023 and February 1, 2021 – January 31, 2022. (8) Contributions include $1.6 million each year for 2023, 2022, and 2021, related to the multiemployer pension fund withdrawal liability. ABF Freight’s multiemployer pension plan obligation with the New England Teamsters and Trucking Industry Pension Fund was restructured under a transition agreement effective on August 1, 2018, which triggered a withdrawal liability settlement to satisfy ABF Freight’s existing potential withdrawal liability obligation to the fund. ABF Freight recognized a one-time charge of $37.9 million (pre-tax) to record the withdrawal liability in second quarter 2018; partially settled the withdrawal liability through the initial lump sum cash payment of $15.1 million made in third quarter 2018; and will settle the remainder with monthly payments over a remaining period of 18 years . (9) Information for this fund was obtained from the annual funding notice, other notices received from the plan, and the Form 5500 filed for the plan years ended September 30, 2022 and 2021. (10) PPA zone status relates to plan years October 1, 2022 – September 30, 2023 and October 1, 2021 – September 30, 2022. (11) Adopted a rehabilitation plan effective January 1, 2009. The plan has been subsequently reviewed and restated effective January 1, 2023. (12) Contribution levels can be impacted by several factors such as changes in business levels and the related time worked by contractual employees, contractual rate increases for pension benefits, and the specific funding structure, which differs among funds. The current and prior collective bargaining agreements and the related supplemental agreements provided for contributions to multiemployer pension plans to be frozen at the current rates for each fund, although certain funds have imposed contribution increases under their rehabilitation or funding improvement plans. The year-over-year changes in multiemployer pension plan contributions presented above were influenced by changes in Asset-Based shipment levels.

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	12 Months Ended
	Dec. 31, 2023
STOCKHOLDERS' EQUITY
Components of accumulated other comprehensive income	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands) Pre-tax amounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net periodic benefit credit ​ $ 6,816 ​ $ 9,287 ​ $ 5,602 ​ Interest rate swap ​ ​ 1,710 ​ ​ 3,526 ​ ​ 419 ​ Foreign currency translation ​ (2,709) ​ (3,247) ​ (1,044) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ $ 5,817 ​ $ 9,566 ​ $ 4,977 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ After-tax amounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net periodic benefit credit ​ $ 5,061 ​ $ 6,896 ​ $ 4,160 ​ Interest rate swap ​ ​ 1,263 ​ ​ 2,604 ​ ​ 309 ​ Foreign currency translation ​ (2,000) ​ (2,397) ​ (770) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ $ 4,324 ​ $ 7,103 ​ $ 3,699 ​
Summary of changes in accumulated other comprehensive income, net of tax, by component	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized ​ ​ Interest Foreign ​ ​ ​ ​ ​ ​ Net Periodic ​ ​ Rate ​ Currency ​ ​ Total Benefit Credit ​ Swap Translation ​ ​ ​ (in thousands) ​ Balances at December 31, 2021 ​ $ 3,699 ​ $ 4,160 ​ $ 309 ​ $ (770) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive income (loss) before reclassifications ​ ​ 3,966 ​ ​ 3,298 ​ ​ 2,295 ​ ​ (1,627) ​ Amounts reclassified from accumulated other comprehensive income ​ ​ (562) ​ ​ (562) ​ ​ — ​ ​ — ​ Net current-period other comprehensive income (loss) ​ ​ 3,404 ​ ​ 2,736 ​ ​ 2,295 ​ ​ (1,627) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balances at December 31, 2022 ​ $ 7,103 ​ $ 6,896 ​ $ 2,604 ​ $ (2,397) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive income (loss) before reclassifications ​ (1,791) ​ (847) ​ ​ (1,341) ​ 397 ​ Amounts reclassified from accumulated other comprehensive income ​ (988) ​ (988) ​ ​ — ​ — ​ Net current-period other comprehensive income (loss) ​ (2,779) ​ (1,835) ​ ​ (1,341) ​ 397 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balances at December 31, 2023 ​ $ 4,324 ​ $ 5,061 ​ $ 1,263 ​ $ (2,000) ​
Summary of the significant reclassifications out of accumulated other comprehensive income (loss) by component	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized Net Periodic ​ ​ ​ Benefit Credit ​ 2023 2022 ​ ​ (in thousands) Amortization of net actuarial gain, pre-tax (1) ​ $ 1,330 ​ $ 757 ​ Tax expense ​ ​ (342) ​ (195) ​ Total, net of tax ​ $ 988 ​ $ 562 ​ (1) Included in the computation of net periodic benefit credit of the Company’s supplemental benefit plan (“SBP”) and postretirement health benefit plan (see Note K). ​
Summary of dividends declared	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 ​ 2022 ​ ​ Per Share Amount Per Share Amount ​ ​ (in thousands, except per share data) First quarter ​ $ 0.12 ​ $ 2,915 ​ $ 0.08 ​ $ 1,978 ​ Second quarter ​ $ 0.12 ​ $ 2,894 ​ $ 0.12 ​ $ 2,949 ​ Third quarter ​ $ 0.12 ​ $ 2,887 ​ $ 0.12 ​ $ 2,965 ​ Fourth quarter ​ $ 0.12 ​ $ 2,846 ​ $ 0.12 ​ $ 2,938 ​

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2023
SHARE-BASED COMPENSATION
Summary of the Company's restricted stock unit award program	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Grant Date ​ ​ ​ Units ​ Fair Value Outstanding – January 1, 2023 ​ 1,023,251 ​ $ 38.83 ​ Granted ​ 149,350 ​ $ 86.53 ​ Vested ​ (381,724) ​ $ 36.04 ​ Forfeited (1) ​ (65,444) ​ $ 51.97 ​ Outstanding – December 31, 2023 ​ 725,433 ​ $ 48.94 ​ (1) Forfeitures are recognized as they occur.
Schedule of restricted stock units granted during the year	The Compensation Committee of the Company’s Board of Directors granted RSUs during the years ended December 31 as follows: ​ k ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Grant Date ​ Units Fair Value 2023 149,350 ​ $ 86.53 ​ 2022 164,739 ​ $ 78.57 ​ 2021 136,295 ​ $ 86.96 ​

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2023
EARNINGS PER SHARE
Schedule of computation of basic and diluted earnings (loss) per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands, except share and per share data) Basic ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income from continuing operations ​ $ 142,164 ​ $ 294,648 ​ $ 210,459 ​ Net income from discontinued operations ​ 53,269 ​ 3,561 ​ 3,062 ​ Net income ​ $ 195,433 ​ $ 298,209 ​ $ 213,521 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares ​ 24,018,801 ​ 24,585,205 ​ 25,471,939 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic earnings per common share ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Continuing operations ​ $ 5.92 ​ $ 11.98 ​ $ 8.26 ​ Discontinued operations ​ ​ 2.22 ​ ​ 0.14 ​ ​ 0.12 ​ Total basic earnings per common share (1) ​ $ 8.14 ​ $ 12.13 ​ $ 8.38 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income from continuing operations ​ $ 142,164 ​ $ 294,648 ​ $ 210,459 ​ Net income from discontinued operations ​ 53,269 ​ 3,561 ​ 3,062 ​ Net income ​ $ 195,433 ​ $ 298,209 ​ $ 213,521 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares ​ ​ 24,018,801 ​ 24,585,205 ​ 25,471,939 ​ Effect of dilutive securities ​ 615,816 ​ 919,303 ​ 1,300,187 ​ Adjusted weighted-average shares and assumed conversions ​ 24,634,617 ​ 25,504,508 ​ 26,772,126 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted earnings per common share ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Continuing operations ​ $ 5.77 ​ $ 11.55 ​ $ 7.86 ​ Discontinued operations ​ ​ 2.16 ​ ​ 0.14 ​ ​ 0.11 ​ Total diluted earnings per common share (1) ​ $ 7.93 ​ $ 11.69 ​ $ 7.98 ​ (1) Earnings per common share is calculated in total and may not equal the sum of earnings per common share from continuing operations and discontinued operations due to rounding. ​

OPERATING SEGMENT DATA (Tables)

OPERATING SEGMENT DATA (Tables)	12 Months Ended
	Dec. 31, 2023
OPERATING SEGMENT DATA
Schedule of reportable operating segment information from continuing operations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands) REVENUES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,871,004 ​ $ 3,010,900 ​ $ 2,573,773 ​ Asset-Light ​ 1,680,645 ​ 2,139,272 ​ 1,300,626 ​ Other and eliminations ​ (124,206) ​ (121,164) ​ (108,214) ​ Total consolidated revenues ​ $ 4,427,443 ​ $ 5,029,008 ​ $ 3,766,185 ​ OPERATING EXPENSES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Salaries, wages, and benefits ​ $ 1,379,756 ​ $ 1,293,487 ​ $ 1,198,253 ​ Fuel, supplies, and expenses ​ 361,355 ​ 378,558 ​ 266,139 ​ Operating taxes and licenses ​ 55,918 ​ 52,290 ​ 49,461 ​ Insurance ​ 52,025 ​ 47,382 ​ 37,800 ​ Communications and utilities ​ 19,288 ​ 18,949 ​ 18,773 ​ Depreciation and amortization ​ 104,165 ​ 97,322 ​ 93,799 ​ Rents and purchased transportation ​ 338,575 ​ 441,167 ​ 364,345 ​ Shared services ​ ​ 279,248 ​ ​ 281,698 ​ ​ 263,532 ​ (Gain) loss on sale of property and equipment and lease impairment charges (1) ​ 982 ​ (12,468) ​ (8,676) ​ Innovative technology costs (2) ​ ​ 21,711 ​ ​ 27,207 ​ ​ 27,631 ​ Other ​ 4,829 ​ 4,175 ​ 2,009 ​ Total Asset-Based ​ 2,617,852 ​ 2,629,767 ​ 2,313,066 ​ Asset-Light ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Purchased transportation ​ 1,435,604 ​ 1,784,668 ​ 1,097,332 ​ Supplies and expenses (3) ​ 12,094 ​ 13,955 ​ 8,661 ​ Depreciation and amortization (4) ​ 20,370 ​ 20,730 ​ 11,387 ​ Shared services ​ ​ 194,296 ​ ​ 218,133 ​ ​ 132,137 ​ Contingent consideration (5) ​ ​ (19,100) ​ ​ 18,300 ​ ​ — ​ Lease impairment charges (6) ​ ​ 14,407 ​ ​ — ​ ​ — ​ Legal settlement (7) ​ ​ 9,500 ​ ​ — ​ ​ — ​ Gain on sale of subsidiary (8) ​ ​ — ​ ​ (402) ​ ​ (6,923) ​ Other (3) ​ ​ 25,745 ​ 31,163 ​ 11,635 ​ Total Asset-Light ​ 1,692,916 ​ 2,086,547 ​ 1,254,229 ​ Other and eliminations ​ (55,944) ​ (81,832) ​ (78,088) ​ Total consolidated operating expenses ​ $ 4,254,824 ​ $ 4,634,482 ​ $ 3,489,207 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ OPERATING INCOME (LOSS) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 253,152 ​ $ 381,133 ​ $ 260,707 ​ Asset-Light ​ (12,271) ​ 52,725 ​ 46,397 ​ Other and eliminations (9) ​ (68,262) ​ (39,332) ​ (30,126) ​ Total consolidated operating income ​ $ 172,619 ​ $ 394,526 ​ $ 276,978 ​ OTHER INCOME (COSTS) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest and dividend income ​ $ 14,728 ​ $ 3,873 ​ $ 1,226 ​ Interest and other related financing costs ​ (9,094) ​ (7,726) ​ (8,914) ​ Other, net (10) ​ 8,662 ​ (2,370) ​ 3,797 ​ Total other income (costs) ​ 14,296 ​ (6,223) ​ (3,891) ​ INCOME BEFORE INCOME TAXES ​ $ 186,915 ​ $ 388,303 ​ $ 273,087 ​ (1) For 2023, includes a $0.7 million noncash lease-related impairment charge for an Asset-Based service center. For 2022, includes a $4.3 million noncash gain on a like-kind property exchange of a service center, with the remaining gains related primarily to sales of replaced equipment. For 2021, includes an $8.6 million gain on the sale of unutilized service center property. (2) Represents costs associated with the freight handling pilot test program at ABF Freight, for which the decision was made to pause the pilot during third quarter 2023. (3) For 2022 and 2021, amounts have been adjusted from those previously reported to reclass certain facility rent expense between line items within the Asset-Light segment. Adjustments made are not material. (4) Depreciation and amortization includes amortization of intangibles associated with acquired businesses. (5) Represents the change in fair value of the contingent earnout consideration to the MoLo acquisition (see Note C). (6) Represents noncash lease-related impairment charges for certain Asset-Light office spaces that were made available for sublease. (7) Represents estimated expenses to settle a claim related to the classification of certain Asset-Light employees under the Fair Labor Standards Act . (8) Gain recognized relates to the sale of the labor services portion of the Asset-Light segment’s moving business in second quarter 2021, including the contingent amount recognized in second quarter 2022 when the funds were released from escrow. (9) For 2023, “Other and eliminations” includes $15.1 million of noncash lease-related impairment charges for a freight handling pilot facility. (10) Includes the components of net periodic benefit cost (credit) other than service cost related to the Company’s SBP and postretirement plans (see Note K) and proceeds and changes in cash surrender value of life insurance policies. For 2023, includes a $3.7 million fair value increase related to the Company’s equity investment in Phantom Auto, based on an observable price change during second quarter 2023 (see Note C). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ 2023 2022 2021 ​ ​ ​ (in thousands) ​ CAPITAL EXPENDITURES, GROSS ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based (1) ​ $ 207,072 ​ $ 137,117 ​ $ 96,180 ​ Asset-Light ​ ​ 7,587 ​ ​ 14,372 ​ ​ 9,565 ​ Other and eliminations (2)(3) ​ 37,752 ​ 77,720 ​ 11,193 ​ ​ ​ $ 252,411 ​ $ 229,209 ​ $ 116,938 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ ​ 2023 2022 2021 ​ ​ ​ (in thousands) ​ DEPRECIATION AND AMORTIZATION EXPENSE (2) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 104,165 ​ $ 97,322 ​ $ 93,799 ​ Asset-Light (4) ​ ​ 20,370 ​ ​ 20,730 ​ ​ 11,387 ​ Other and eliminations (2) ​ 20,814 ​ 20,107 ​ 17,374 ​ ​ ​ $ 145,349 ​ $ 138,159 ​ $ 122,560 ​ (1) Includes assets acquired through notes payable of $33.5 million, $79.0 million, and $59.7 million in 2023, 2022, and 2021, respectively. (2) Other and eliminations includes certain assets held for the benefit of multiple segments, including information systems equipment. For 2022, also includes the purchase of a property for $37.5 million. Depreciation and amortization associated with these assets is allocated to the reporting segments. Depreciation and amortization expense includes amortization of internally developed capitalized software which has not been included in gross capital expenditures presented in the table. (3) Includes assets acquired through notes payable of $3.4 million in 2022. (4) Includes amortization of intangibles of $12.8 million, $12.9 million, and $5.3 million in 2023, 2022, and 2021, respectively.
Schedule of revenues from customers and intersegment revenues	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands) Revenues from customers ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,749,803 ​ $ 2,896,284 ​ $ 2,470,529 ​ Asset-Light ​ 1,673,399 ​ 2,128,394 ​ 1,291,679 ​ Other ​ 4,241 ​ 4,330 ​ 3,977 ​ Total consolidated revenues ​ $ 4,427,443 ​ $ 5,029,008 ​ $ 3,766,185 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Intersegment revenues ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 121,201 ​ $ 114,616 ​ $ 103,244 ​ Asset-Light ​ ​ 7,246 ​ ​ 10,878 ​ ​ 8,947 ​ Other and eliminations ​ ​ (128,447) ​ ​ (125,494) ​ ​ (112,191) ​ Total intersegment revenues ​ $ — ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total segment revenues ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,871,004 ​ ​ 3,010,900 ​ $ 2,573,773 ​ Asset-Light ​ ​ 1,680,645 ​ ​ 2,139,272 ​ ​ 1,300,626 ​ Other and eliminations ​ ​ (124,206) ​ ​ (121,164) ​ ​ (108,214) ​ Total consolidated revenues ​ $ 4,427,443 ​ $ 5,029,008 ​ $ 3,766,185 ​
Schedule of consolidated operating expenses by component	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023 2022 2021 ​ ​ (in thousands) ​ OPERATING EXPENSES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Salaries, wages, and benefits ​ $ 1,781,304 ​ $ 1,728,653 ​ $ 1,527,533 ​ Rents, purchased transportation, and other costs of services ​ 1,642,669 ​ 2,100,663 ​ 1,349,106 ​ Fuel, supplies, and expenses (1) ​ 479,688 ​ 488,009 ​ 360,657 ​ Depreciation and amortization (2) ​ 145,349 ​ 138,159 ​ 122,560 ​ Contingent consideration (3) ​ ​ (19,100) ​ ​ 18,300 ​ ​ — ​ Lease impairment charges (4) ​ ​ 30,162 ​ ​ — ​ ​ — ​ Other (1)(5) ​ 194,752 ​ 160,698 ​ 129,351 ​ ​ ​ $ 4,254,824 ​ $ 4,634,482 ​ $ 3,489,207 ​ (1) For 2022 and 2021, amounts have been adjusted from those previously reported to reclass certain facility rent expense between line items within the Asset-Light segment. Adjustments made are not material. (2) Includes amortization of intangibles assets. (3) Represents the change in fair value of the contingent earnout consideration related to the MoLo acquisition (see Notes C and E). (4) Represents noncash lease-related impairment charges for a freight handling pilot facility, a service center, and office spaces that were made available for sublease. (5) For 2023, includes estimated expenses of $9.5 million to settle a claim related to the classification of certain Asset-Light employees under the Fair Labor Standards Act . For 2022, includes a $12.5 million gain related to the sale of property and equipment within the Asset-Based segment and the sale of replaced equipment and a like-kind exchange of a service center property in the prior year. For 2021, includes a $6.9 million gain related to the sale of a subsidiary within the Asset-Light segment and an $8.6 million gain related to the sale of an unutilized service center property within the Asset-Based segment. For 2023, 2022, and 2021, also includes innovative technology costs of $52.4 million, $40.8 million, and $32.8 million, respectively, associated with the freight handling pilot program at ABF Freight, costs related to the Company’s customer pilot offering of Vaux TM , and initiatives to optimize performance through technological innovation.

ORGANIZATION AND DESCRIPTION _2

ORGANIZATION AND DESCRIPTION OF THE BUSINESS AND FINANCIAL STATEMENT PRESENTATION - Organization (Details)	12 Months Ended
	Dec. 31, 2023 segment
Organization and description of business
Number of reportable operating segments	2
Asset Based
Organization and description of business
Percentage of the Company's revenues, before other revenues and intercompany eliminations, represented by the Asset-Based segment	63%
Asset Based | Unionized employees concentration risk | Number of employees
Organization and description of business
Percentage of Asset-Based segment employees covered under collective bargaining agreement with the IBT	82%

ORGANIZATION AND DESCRIPTION _3

ORGANIZATION AND DESCRIPTION OF THE BUSINESS AND FINANCIAL STATEMENT PRESENTATION - Discontinued Operations (Details) $ in Millions	Feb. 28, 2023 USD ($)
FleetNet | Discontinued Operations, Disposed of by Sale
Discontinued Operations
Aggregate purchase price	$ 100.9

ACCOUNTING POLICIES - Concentra

ACCOUNTING POLICIES - Concentration (Details) - Minimum	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues | Customer concentration risk
Concentrations
Percentage for concentration of credit risk disclosure	2%	2%	2%
Accounts receivable | Credit concentration risk
Concentrations
Percentage for concentration of credit risk disclosure	5%	5%

ACCOUNTING POLICIES - Allowance

ACCOUNTING POLICIES - Allowances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Allowances
Allowance for credit losses on trade accounts receivable	$ 5.5	$ 9.3
Increase in amount of allowance for credit losses	3.6
Write-offs, net of recoveries	$ 7.4

ACCOUNTING POLICIES - Property

ACCOUNTING POLICIES - Property (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment
Lease impairment charges	$ 30,200	$ 30,162
Other long-term assets
Property, Plant and Equipment
Assets held for sale		$ 1,500	$ 800
Structures | Minimum
Property, Plant and Equipment
Depreciation/amortization period		15 years
Structures | Maximum
Property, Plant and Equipment
Depreciation/amortization period		60 years
Revenue Equipment | Minimum
Property, Plant and Equipment
Depreciation/amortization period		3 years
Revenue Equipment | Maximum
Property, Plant and Equipment
Depreciation/amortization period		22 years
Service, office, and other equipment | Minimum
Property, Plant and Equipment
Depreciation/amortization period		2 years
Service, office, and other equipment | Maximum
Property, Plant and Equipment
Depreciation/amortization period		16 years
Software | Minimum
Property, Plant and Equipment
Depreciation/amortization period		2 years
Software | Maximum
Property, Plant and Equipment
Depreciation/amortization period		7 years

ACCOUNTING POLICIES - Long Term

ACCOUNTING POLICIES - Long Term Investments (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
ACCOUNTING POLICIES
Change in fair value included in operating income	$ 3,700	$ 3,739
Carrying value of equity securities without readily determinable fair value		$ 28,700	$ 25,000

ACCOUNTING POLICIES - Book Over

ACCOUNTING POLICIES - Book Overdrafts (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Accounts Payable
Book Overdrafts
Amount of book overdrafts	$ 19.2	$ 30.3

ACCOUNTING POLICIES - Other Rec

ACCOUNTING POLICIES - Other Recognition and Disclosure (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Recognition and Disclosure
Pension settlement expense, pre-tax	$ 0	$ 0	$ 0
Revenue, Practical Expedient, Incremental Cost of Obtaining Contract	true
Revenue, Practical Expedient, Remaining Performance Obligation	true

ACCOUNTING POLICIES - Accelerat

ACCOUNTING POLICIES - Accelerated Share Repurchase (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Nov. 02, 2021	Jan. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Equity
Cost of repurchased shares			$ 91,531	$ 65,002	$ 83,100
Accelerated Share Repurchase Agreement ("ASR")
Equity
Amount paid in accelerated repurchase	$ 100,000
Number of shares repurchased during the period	709,287	214,763
Cost of repurchased shares	$ 75,000
Amount of unsettled forward contract classified within stockholders' equity as additional paid in capital.					$ 25,000

ACCOUNTING POLICIES - Share-Bas

ACCOUNTING POLICIES - Share-Based Compensation (Details) - Restricted Stock Units	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee
Share-Based Compensation
Vesting period	3 years	3 years	3 years	4 years	4 years	4 years
Percentage of stock awards vesting each year.	33.30%	33.30%
Nonemployee Director
Share-Based Compensation
Vesting period	1 year

FINANCIAL INSTRUMENTS AND FAI_3

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Cash and Cash Equivalents and Short-term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair value disclosure
Cash and cash equivalents	$ 262,226	$ 158,264
Short-term investments	67,842	167,662
Concentrations of Credit Risk of Financial Instruments
Cash deposits and short-term investments which were neither FDIC insured nor direct obligations of the U.S. government	76,300	87,600
Cash deposits
Fair value disclosure
Cash and cash equivalents	168,472	137,247
Variable rate demand notes
Fair value disclosure
Cash and cash equivalents		9,285
Money market funds
Fair value disclosure
Cash and cash equivalents	93,754	11,732
Certificates of deposit
Fair value disclosure
Short-term investments	$ 67,842	88,851
U.S. Treasury securities
Fair value disclosure
Short-term investments		$ 78,811

FINANCIAL INSTRUMENTS AND FAI_4

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Financial instruments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Carrying Value
Fair value disclosure
Financial instruments	$ 248,340	$ 284,723
Fair Value | Level 2
Fair value disclosure
Financial instruments	245,369	276,689
Credit Facility | Carrying Value
Fair value disclosure
Financial instruments	50,000	50,000
Credit Facility | Fair Value | Level 2
Fair value disclosure
Financial instruments	50,000	50,000
Notes payable | Carrying Value
Fair value disclosure
Financial instruments	178,938	214,623
Notes payable | Fair Value | Level 2
Fair value disclosure
Financial instruments	177,149	207,778
New England Pension Fund withdrawal liability
Fair value disclosure
Outstanding withdrawal liability	19,400
New England Pension Fund withdrawal liability | Accrued expenses
Fair value disclosure
Outstanding withdrawal liability	700
New England Pension Fund withdrawal liability | Carrying Value
Fair value disclosure
Financial instruments	19,402	20,100
New England Pension Fund withdrawal liability | Fair Value | Level 2
Fair value disclosure
Financial instruments	$ 18,220	$ 18,911
Measurement input	0.053	0.053
Financial Instrument, Measurement Input	Discount Rate	Discount Rate

FINANCIAL INSTRUMENTS AND FAI_5

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Assets and Liabilities (Details) $ in Thousands	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Liabilities:
Contingent consideration, noncurrent	$ 92,900	$ 112,000
Discount Rate | Valuation Technique, Discounted Cash Flow
Liabilities:
Measurement input	0.133	0.140
Recurring basis
Assets:
Assets	$ 100,091	$ 19,240
Liabilities:
Contingent consideration, noncurrent	92,900	112,000
Liabilities	92,900	112,000
Recurring basis | Cash and cash equivalents
Assets:
Money market funds	93,754	11,732
Recurring basis | Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	4,627	3,982
Interest rate swap	1,710	3,526
Recurring basis | Level 1
Assets:
Assets	98,381	15,714
Recurring basis | Level 1 | Cash and cash equivalents
Assets:
Money market funds	93,754	11,732
Recurring basis | Level 1 | Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	4,627	3,982
Recurring basis | Level 2
Assets:
Assets	1,710	3,526
Recurring basis | Level 2 | Other long-term assets
Assets:
Interest rate swap	1,710	3,526
Recurring basis | Level 3
Liabilities:
Contingent consideration, noncurrent	92,900	112,000
Liabilities	$ 92,900	$ 112,000

FINANCIAL INSTRUMENTS AND FAI_6

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Changes in Fair Value of Liabilities (Details) - Contingent Consideration $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Changes in fair value
Balance at beginning of period	$ 112,000
Change in fair value included in operating income	$ (19,100)
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income	Operating income
Balance at end of period	$ 92,900

FINANCIAL INSTRUMENTS AND FAI_7

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Assets Measured at Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2023
Fair value measurement
Equity investment, Balance at beginning of period		$ 25,000
Change in fair value included in operating income	$ 3,700	3,739
Equity investment, Balance at end of period		28,700
Nonrecurring basis | Level 3
Fair value measurement
Equity investment, Balance at beginning of period		25,000
Change in fair value included in operating income		3,739
Equity investment, Balance at end of period		$ 28,739

FINANCIAL INSTRUMENTS AND FAI_8

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Impairment (Details) $ in Thousands		3 Months Ended	12 Months Ended
	Sep. 01, 2023	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair value measurement
Operating right-of-use assets, Lease impairment charges			$ (28,124)
Leasehold improvements, Lease impairment charges			(2,038)
Operating right-of-use assets and Leasehold improvements, Lease impairment charges		$ (30,200)	(30,162)
Nonrecurring basis
Fair value measurement
Assets				$ 0
Carrying Value | Nonrecurring basis
Fair value measurement
Operating right-of-use assets			48,417
Leasehold improvements			3,874
Operating right-of-use assets and Leasehold improvements			52,291
Fair Value | Nonrecurring basis | Level 3
Fair value measurement
Operating right-of-use assets			20,293
Leasehold improvements			1,836
Operating right-of-use assets and Leasehold improvements			$ 22,129
Operating Right-Of-Use Assets and Leasehold Improvements, Valuation Technique	Valuation Technique, Discounted Cash Flow
Operating Right-Of-Use Assets and Leasehold Improvements, Measurement Input	Discount Rate
Fair Value | Nonrecurring basis | Level 3 | Minimum
Fair value measurement
Operating right-of-use assets and Leasehold improvements, Measurement input	0.075
Fair Value | Nonrecurring basis | Level 3 | Maximum
Fair value measurement
Operating right-of-use assets and Leasehold improvements, Measurement input	0.095

DISCONTINUED OPERATIONS - Finan

DISCONTINUED OPERATIONS - Financial results (Details) - USD ($) $ in Thousands		12 Months Ended
	Feb. 28, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating expenses
(Gain) loss on sale of business		$ (70,201)
Income tax provision (benefit)		18,255	$ 1,291	$ 1,005
Income (loss) from discontinued operations, net of tax		$ 53,269	3,561	3,062
FleetNet | Discontinued Operations, Disposed of by Sale
Discontinued Operations
Aggregate purchase price	$ 100,900
Gain on sale of discontinued operations, net of tax	52,300
Discontinued Operation Gain Loss On Disposal Statement Of Income Or Comprehensive Income Extensible Enumeration Not Disclosed Flag		true
Financial results from discontinued operations
Revenues		$ 55,929
Operating expenses
(Gain) loss on sale of business	$ (70,200)	(70,201)
Other		54,623
Operating expenses		(15,578)
Operating Income (loss)		71,507
Other income, net		17
Income (loss) from discontinued operations before income taxes		71,524
Income tax provision (benefit)		18,255
Income (loss) from discontinued operations, net of tax		53,269
Transaction costs		$ 3,800
FleetNet | Discontinued Operations, Held-for-sale
Financial results from discontinued operations
Revenues			295,043	213,882
Operating expenses
Other			290,300	209,874
Operating expenses			290,300	209,874
Operating Income (loss)			4,743	4,008
Other income, net			109	59
Income (loss) from discontinued operations before income taxes			4,852	4,067
Income tax provision (benefit)			1,291	1,005
Income (loss) from discontinued operations, net of tax			$ 3,561	$ 3,062

DISCONTINUED OPERATIONS - Asset

DISCONTINUED OPERATIONS - Assets and liabilities (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Assets and liabilities from discontinued operations
Total current assets of discontinued operations	$ 64,736
Total long-term assets of discontinued operations	11,097
Total current liabilities of discontinued operations	51,665
Total long-term liabilities of discontinued operations	781
FleetNet | Discontinued Operations, Held-for-sale
Assets and liabilities from discontinued operations
Cash and cash equivalents	108
Accounts receivable, net	63,022
Other current assets	1,606
Total current assets of discontinued operations	64,736
Property, plant and equipment, net	10,350
Goodwill	630
Intangible assets, net	63
Other long-term assets	54
Total long-term assets of discontinued operations	11,097
Accounts payable	47,687
Income taxes payable	613
Accrued expenses	3,365
Total current liabilities of discontinued operations	51,665
Deferred tax liability	781
Total long-term liabilities of discontinued operations	$ 781

DISCONTINUED OPERATIONS - Cash

DISCONTINUED OPERATIONS - Cash flows (Details) - FleetNet - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Discontinued Operations, Disposed of by Sale
Cash flows from discontinued operations
Net cash provided by operating activities	$ 762
Net cash used in investing activities	(397)
Net cash provided by (used in) financing activities	(473)
Net increase (decrease) in cash and cash equivalents	(108)
Depreciation and amortization expense	400
Share-based compensation expense	300
Purchases of property, plant and equipment	$ 100
Discontinued Operations, Held-for-sale
Cash flows from discontinued operations
Net cash provided by operating activities		$ 2,825
Net cash used in investing activities		(3,329)
Net cash provided by (used in) financing activities		560
Net increase (decrease) in cash and cash equivalents		56
Depreciation and amortization expense		1,900
Purchases of property, plant and equipment		$ 1,400

ACQUISITION - MoLo (Details)

ACQUISITION - MoLo (Details) - USD ($) $ in Thousands	12 Months Ended			14 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2022	Nov. 01, 2021
Purchase Consideration
Business acquisition, net of cash acquired		$ (2,279)	$ 239,380
MoLo Solutions, LLC
Purchase Consideration
Business acquisition, net of cash acquired				$ 237,100
Business acquisition, cash acquired		$ 2,300
Earnout payment	$ 0
Contingent consideration, target earnout payment for 2024	70,000
Contingent consideration, target earnout payment for 2025	$ 145,000
MoLo Solutions, LLC | 100% of target
Purchase Consideration
Adjusted EBITDA target percentage					100%
Contingent consideration, target					$ 215,000
MoLo Solutions, LLC | 80% of target
Purchase Consideration
Adjusted EBITDA target percentage					80%
Contingent consideration, low range					$ 95,000
MoLo Solutions, LLC | 300% of target
Purchase Consideration
Adjusted EBITDA target percentage					300%
Contingent consideration, high range					$ 455,000

ACQUISITION - Revenue and expen

ACQUISITION - Revenue and expenses (Details) - USD ($) $ in Thousands	2 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Business Acquisition
Revenues		$ 4,427,443	$ 5,029,008	$ 3,766,185
Operating income (loss)		$ 172,619	$ 394,526	276,978
MoLo Solutions, LLC
Business Acquisition
Revenues	$ 120,300
Operating income (loss)	$ (1,200)
Acquisition related costs				$ 6,000

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details) - USD ($) $ in Thousands			12 Months Ended
	Oct. 01, 2023	Oct. 01, 2022	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2021
Goodwill by reportable operating segment
Goodwill			$ 304,753	$ 304,753	$ 299,708
Purchase accounting adjustment			5,045
Accumulated impairment			(20,000)	$ (20,000)
FleetNet Segment | Discontinued Operations, Held-for-sale
Goodwill by reportable operating segment
Goodwill, Discontinued operation			$ 600		$ 600
Asset-Light
Goodwill by reportable operating segment
Goodwill impairment	$ 0	$ 0

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Intangible (Details) - USD ($) $ in Thousands	Oct. 01, 2023	Oct. 01, 2022	Dec. 31, 2023	Dec. 31, 2022
Finite-lived intangible assets
Weighted Average Amortization Period			11 years
Cost			$ 129,730	$ 129,493
Accumulated Amortization			60,880	48,060
Net Value			68,850	81,433
Total intangible assets
Cost			162,030	161,793
Net Value			101,150	113,733
Impairment Assessment of Intangible Assets
Impairment of indefinite-lived intangible asset	$ 0	$ 0
Trade name
Indefinite-lived intangible asset
Net Value			$ 32,300	32,300
Customer relationships
Finite-lived intangible assets
Weighted Average Amortization Period			12 years
Cost			$ 99,579	99,579
Accumulated Amortization			51,357	42,933
Net Value			$ 48,222	56,646
Other intangible assets
Finite-lived intangible assets
Weighted Average Amortization Period			8 years
Cost			$ 30,151	29,914
Accumulated Amortization			9,523	5,127
Net Value			$ 20,628	$ 24,787

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS - Amortization (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Future amortization for intangible assets
2024	$ 12,790
2025	12,790
2026	8,683
2027	7,258
2028	7,259
Thereafter	20,070
Net Value	$ 68,850	$ 81,433

INCOME TAXES - Provision (Detai

INCOME TAXES - Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current provision on continuing operations:
Federal	$ 38,860	$ 79,477	$ 55,684
State	10,949	19,713	14,229
Foreign	508	869	341
Total current provision on continuing operation	50,317	100,059	70,254
Deferred (benefit) on continuing operations:
Federal	(4,882)	(5,591)	(6,119)
State	(682)	(793)	(1,570)
Foreign	(2)	(20)	63
Deferred tax benefit	(5,566)	(6,404)	(7,626)
Total provision for income taxes	44,751	93,655	62,628
Current provision on discontinued operations:
Federal	14,656	901	767
State	3,599	236	201
Total current provision on discontinued operations	18,255	1,137	968
Deferred provision on discontinued operations:
Federal		114	21
State		40	16
Total deferred provision on discontinued operations		154	37
Total provision for income taxes on discontinued operations	18,255	1,291	1,005
Total provision for income taxes, Continuing and discontinued operations	$ 63,006	$ 94,946	$ 63,633

INCOME TAXES - Deferred income

INCOME TAXES - Deferred income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Components of the deferred tax provision or benefit
Amortization, depreciation, and basis differences for property, plant and equipment and other long-lived assets	$ 1,744	$ 4,274	$ 1,409
Amortization of intangibles	6,127	(2,995)	(555)
Changes in reserves for workers' compensation, third-party casualty, and cargo claims	(4,975)	(3,713)	(3,296)
Revenue recognition	(50)	6	(1,434)
Allowance for credit losses	1,094	(388)	170
Nonunion pension and other retirement plans	(3)	(4)	(3)
Multiemployer pension fund withdrawal	180	172	164
Federal and state net operating loss carryforwards utilized (generated)	(758)	899	(300)
State depreciation adjustments	(456)	(915)	598
Share-based compensation	531	737	(949)
Valuation allowance increase (decrease)	44	(489)	912
Other accrued expenses	(2,143)	(3,069)	(4,056)
Prepaid expenses	313	(18)	(788)
Operating lease right-of-use assets/liabilities - net	(8,065)	(651)	(228)
Other	851	(250)	730
Deferred tax benefit	$ (5,566)	$ (6,404)	$ (7,626)

INCOME TAXES - Deferred (Detail

INCOME TAXES - Deferred (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Accrued expenses	$ 60,842	$ 53,785
Operating lease right-of-use liabilities	53,589	46,056
Supplemental pension liabilities	85	81
Multiemployer pension fund withdrawal	4,871	5,063
Postretirement liabilities other than pensions	3,389	3,137
Share-based compensation	5,249	5,622
Federal and state net operating loss carryforwards	1,511	753
Receivable allowances	1,951	2,967
Other	709	417
Total deferred tax assets	132,196	117,881
Valuation allowance	(1,751)	(1,707)
Total deferred tax assets, net of valuation allowance	130,445	116,174
Deferred tax liabilities:
Amortization, depreciation, and basis differences for property, plant and equipment, and other long-lived assets	118,211	116,290
Operating lease right-of-use assets	43,938	44,170
Intangibles	10,256	4,442
Prepaid expenses	5,685	5,424
Total deferred tax liabilities	178,090	170,326
Net deferred tax liabilities	$ (47,645)	$ (54,152)

INCOME TAXES - Rate Reconciliat

INCOME TAXES - Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation between the effective income tax rate, as computed on income from continuing operations before income taxes, and the statutory federal income tax rate
Statutory federal rate (as a percent)	21%	21%	21%
Income tax provision at the statutory federal rate	$ 39,252	$ 81,544	$ 57,348
Federal income tax effects of:
State income taxes	(2,156)	(3,973)	(2,658)
Nondeductible expenses	4,040	5,606	3,596
Life insurance proceeds and changes in cash surrender value	(962)	575	(866)
Alternative fuel tax credit	(1,302)	(2,449)
Net increase (decrease) in valuation allowances	44	(464)	887
Net increase in uncertain tax positions			854
Settlement of share-based compensation	(3,989)	(6,693)	(6,021)
Foreign tax credits generated	(506)	(849)	(404)
Federal research and development tax credits	(75)	278	(2,044)
Other	(368)	311	(1,127)
Federal income tax provision	33,978	73,886	49,565
State income tax provision	10,267	18,920	12,659
Foreign income tax provision	506	849	404
Total provision for income taxes	$ 44,751	$ 93,655	$ 62,628
Effective tax rate (as a percent)	23.90%	24.10%	22.90%

INCOME TAXES - Tax Rate (Detail

INCOME TAXES - Tax Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
INCOME TAXES
Effective tax rate, including discontinued operations (as a percent)	24.40%	24.10%	23%
Effective tax rate from discontinued operations (as a percent)	25.50%	26.60%	24.70%
State tax, low end of range of rate (as a percent)	6%
State tax, high end of range of rate (as a percent)	6.50%
Income taxes paid, excluding income tax refunds	$ 115.7	$ 148.7	$ 77.5
Income tax refunds	$ 36.4	$ 42.3	$ 19.4

INCOME TAXES - Stock Compensati

INCOME TAXES - Stock Compensation (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
INCOME TAXES
Tax benefit for settlement of stock awards (as a percent)	2.80%	2.10%	2.80%

INCOME TAXES - NOL (Details)

INCOME TAXES - NOL (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) Y	Dec. 31, 2022 USD ($)
Federal
Operating loss carryforwards
Operating loss carryforwards	$ 0.6
State
Operating loss carryforwards
Operating loss carryforwards	26.4
Valuation allowance, NOLs	0.5	$ 0.4
State tax department of Panther
Operating loss carryforwards
Operating loss carryforwards	1.4
State tax department of other subsidiaries
Operating loss carryforwards
Operating loss carryforwards	$ 9.7
Number of prior years with taxable losses | Y	3
Minimum | State tax department of Panther
Operating loss carryforwards
Carryforward expiration period	10 years
Maximum | State tax department of Panther
Operating loss carryforwards
Carryforward expiration period	20 years

INCOME TAXES - Tax Credit Carry

INCOME TAXES - Tax Credit Carryforward (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Foreign
Tax credit carryforwards
Valuation allowance, tax credit carryforwards	$ 1	$ 1
Research and development | State
Tax credit carryforwards
Valuation allowance, tax credit carryforwards	0.2	0.2
Interest expense carryforwards | State | Maximum
Tax credit carryforwards
Valuation allowance, tax credit carryforwards	$ 0.1	$ 0.1

INCOME TAXES - Uncertain Tax Po

INCOME TAXES - Uncertain Tax Positions (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Income taxes
Reserve for uncertain tax positions		$ 0.9	$ 0.9
Forecast
Income taxes
Reversal of uncertain tax position	$ 0.5

LEASES - Lease terms (Details)

LEASES - Lease terms (Details)	12 Months Ended
	Dec. 31, 2023
Operating leases
Option to renew	true
Early termination option	true
Notification period for early termination of operating lease	24 months
Maximum
Operating leases
Remaining lease terms	9 years 9 months 18 days
Operating lease, renewal term	10 years

LEASES - Components of Lease Ex

LEASES - Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
LEASES
Operating lease expense	$ 38,794	$ 31,790	$ 26,552
Variable lease expense	6,804	4,188	4,128
Sublease income	(246)	(391)	(626)
Total operating lease expense	$ 45,352	$ 35,587	$ 30,054

LEASES - Cash Flows (Details)

LEASES - Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating leases
Noncash change in operating right-of-use assets	$ 33,470	$ 27,465	$ 24,023
Change in operating lease liabilities	(30,550)	(24,513)	(23,400)
Operating right-of-use assets and lease liabilities, net	2,920	2,952	623
Cash paid for amounts included in the measurement of operating lease liabilities	$ (35,759)	$ (28,830)	$ (25,909)

LEASES - Supplemental Balance S

LEASES - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating leases
Operating right-of-use assets (long-term)	$ 169,999	$ 166,515
Operating lease liabilities (current)	32,172	26,225
Operating lease liabilities (long-term)	176,621	147,828
Total operating lease liabilities	$ 208,793	$ 174,053
Operating Lease, Liability, Statement of Financial Position	Operating lease liabilities (current), Operating lease liabilities (long-term)	Operating lease liabilities (current), Operating lease liabilities (long-term)
Weighted average remaining lease term (in years)	7 years 4 months 24 days	7 years 7 months 6 days
Weighted average discount rate	4.29%	3.58%
Land And Structures
Operating leases
Operating right-of-use assets (long-term)	$ 169,663	$ 165,822
Operating lease liabilities (current)	31,865	25,824
Operating lease liabilities (long-term)	176,598	147,534
Total operating lease liabilities	208,463	173,358
Equipment and Other
Operating leases
Operating right-of-use assets (long-term)	336	693
Operating lease liabilities (current)	307	401
Operating lease liabilities (long-term)	23	294
Total operating lease liabilities	$ 330	$ 695

LEASES - Maturities of Operatin

LEASES - Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Maturities of operating lease liabilities
2024	$ 40,218
2025	36,458
2026	33,187
2027	27,071
2028	24,033
Thereafter	86,011
Total lease payments	246,978
Less imputed interest	(38,185)
Total operating lease liabilities	$ 208,793	$ 174,053
Operating Lease, Liability, Statement of Financial Position	Operating lease liabilities (current), Operating lease liabilities (long-term)	Operating lease liabilities (current), Operating lease liabilities (long-term)
Future minimum payments for leases that have not yet commenced	$ 28,800
Lease term for lease commitments that have not yet commenced	10 years
Land And Structures
Maturities of operating lease liabilities
2024	$ 39,905
2025	36,435
2026	33,187
2027	27,071
2028	24,033
Thereafter	86,011
Total lease payments	246,642
Less imputed interest	(38,179)
Total operating lease liabilities	208,463	$ 173,358
Equipment and Other
Maturities of operating lease liabilities
2024	313
2025	23
Total lease payments	336
Less imputed interest	(6)
Total operating lease liabilities	$ 330	$ 695

LEASES - Impairment (Details)

LEASES - Impairment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2023
LEASES
Lease impairment charges	$ 30,200	$ 30,162
Operating right-of-use assets, Lease impairment charges		$ 28,124

LONG-TERM DEBT AND FINANCING _3

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Long-term debt obligations
Long-term debt	$ 228,938	$ 264,623
Less current portion	66,948	66,252
Long-term debt, less current portion	$ 161,990	198,371
Weighted-average interest rate (as a percent)	3.30%
Credit Facility
Long-term debt obligations
Long-term debt	$ 50,000	50,000
Interest rate (as a percent)	6.60%
Credit Facility | Interest rate swap agreement
Long-term debt obligations
Amount of borrowings covered by the interest rate swap	$ 50,000	$ 50,000
Effective fixed interest rate on hedged borrowings (as a percent)	1.55%	1.55%
Notes payable
Long-term debt obligations
Long-term debt	$ 178,938	$ 214,623
Weighted-average interest rate (as a percent)	3.80%

LONG-TERM DEBT AND FINANCING _4

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Maturities of long-term debt obligations
2024	$ 75,800
2025	53,388
2026	41,476
2027	74,972
2028	5,520
Total payments	251,156
Less amounts representing interest	22,218
Long-term debt	228,938	$ 264,623
Credit Facility
Maturities of long-term debt obligations
2024	3,021
2025	2,353
2026	2,211
2027	51,688
Total payments	59,273
Less amounts representing interest	9,273
Long-term debt	50,000	50,000
Notes payable
Maturities of long-term debt obligations
2024	72,779
2025	51,035
2026	39,265
2027	23,284
2028	5,520
Total payments	191,883
Less amounts representing interest	12,945
Long-term debt	$ 178,938	$ 214,623

LONG-TERM DEBT AND FINANCING _5

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Assets Securing Notes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Financing Arrangements
Total assets securing notes payable	$ 339,060	$ 336,222
Less accumulated depreciation	135,305	119,244
Net assets securing notes payable	$ 203,755	216,978
Weighted-average interest rate (as a percent)	3.30%
Interest paid, net of capitalized interest	$ 8,700	7,100	$ 8,700
Capitalized interest	300	300	$ 500
Revenue Equipment
Financing Arrangements
Total assets securing notes payable	300,922	294,700
Service, office, and other equipment
Financing Arrangements
Total assets securing notes payable	$ 38,138	$ 41,522

LONG-TERM DEBT AND FINANCING _6

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Credit Facility (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2022
Financing Arrangements
Repayment of debt	$ 69,180	$ 115,540	$ 171,915
Credit Facility
Financing Arrangements
Maximum borrowing capacity	250,000
Additional borrowing capacity that may be requested	125,000
Remaining borrowing capacity	$ 200,000
Credit Facility | Alternate Base Rate | Minimum
Financing Arrangements
Basis spread (as a percent)	0.125%
Credit Facility | Alternate Base Rate | Maximum
Financing Arrangements
Basis spread (as a percent)	1%
Credit Facility | Adjusted Term SOFR Screen Rate
Financing Arrangements
Variable rate adjustment (as a percent)	0.10%
Credit Facility | Adjusted Term SOFR Screen Rate | Minimum
Financing Arrangements
Basis spread (as a percent)	1.125%
Credit Facility | Adjusted Term SOFR Screen Rate | Maximum
Financing Arrangements
Basis spread (as a percent)	2%
Swing Line Facility
Financing Arrangements
Maximum borrowing capacity	$ 40,000	$ 40,000		$ 25,000
Letters of Credit, Sub-Facility
Financing Arrangements
Maximum borrowing capacity	$ 20,000

LONG-TERM DEBT AND FINANCING _7

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Interest Rate Swap (Details) - Interest rate swap agreement, maturing on October 1, 2024 - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Oct. 31, 2022	Jun. 30, 2022
Financing Arrangements
Notional amount				$ 50
Fixed interest rate payments (as a percent)			0.33%
Other long-term assets
Financing Arrangements
Fair value of interest rate swap, asset	$ 1.7	$ 3.5

LONG-TERM DEBT AND FINANCING _8

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Securitization Program (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Financing Arrangements
Outstanding letters of credit	$ 17.4	$ 10.6
Accounts receivable securitization program
Financing Arrangements
Maximum borrowing capacity	50
Additional borrowing capacity that may be requested	100
Outstanding letters of credit	16.8	$ 10
Remaining borrowing capacity	$ 33.2

LONG-TERM DEBT AND FINANCING _9

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Letters of Credit & Surety Bonds (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Financing Arrangements
Outstanding letters of credit	$ 17.4	$ 10.6
Accounts receivable securitization program
Financing Arrangements
Outstanding letters of credit	16.8	10
Surety bonds
Financing Arrangements
Outstanding surety bonds under uncollateralized bond programs	$ 65.2	$ 62.6

LONG-TERM DEBT AND FINANCING_10

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Notes Payable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Notes payable | Revenue Equipment
Financing Arrangements
Assets financed during the period under promissory note arrangements	$ 33.5	$ 82.4

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
ACCRUED EXPENSES.
Workers' compensation, third-party casualty, and loss and damage claims reserves	$ 189,948	$ 133,122
Accrued vacation pay	63,183	58,875
Accrued compensation, including retirement benefits	87,851	119,836
Taxes other than income	10,743	11,375
Other	26,304	15,249
Total accrued expenses	$ 378,029	$ 338,457

EMPLOYEE BENEFIT PLANS - Plan s

EMPLOYEE BENEFIT PLANS - Plan summary (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
POSTRETIREMENT BENEFIT PLANS
Noncash charge to pension settlement expense	$ 0	$ 0	$ 0

EMPLOYEE BENEFIT PLANS - Funded

EMPLOYEE BENEFIT PLANS - Funded status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Supplemental Benefit Plan
Change in benefit obligations
Benefit obligations at beginning of period	$ 338	$ 381
Interest cost	16	7	$ 4
Actuarial (gain) loss	4	(50)
Benefit obligations at end of period	358	338	381
Change in plan assets
Funded status at period end	(358)	(338)
Accumulated benefit obligation	358	338
Postretirement Health Benefit Plan
Change in benefit obligations
Benefit obligations at beginning of period	12,534	16,992
Service cost	78	156	192
Interest cost	599	441	427
Actuarial (gain) loss	1,137	(4,392)
Benefits paid	(680)	(663)
Benefit obligations at end of period	13,668	12,534	$ 16,992
Change in plan assets
Employer contributions	680	663
Benefits paid	(680)	(663)
Funded status at period end	(13,668)	(12,534)
Accumulated benefit obligation	$ 13,668	$ 12,534

EMPLOYEE BENEFIT PLANS - Recogn

EMPLOYEE BENEFIT PLANS - Recognized in Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Amounts recognized in the consolidated balance sheets
Pension and postretirement liabilities, less current portion	$ (13,319)	$ (12,196)
Supplemental Benefit Plan
Amounts recognized in the consolidated balance sheets
Pension and postretirement liabilities, less current portion	(358)	(338)
Liabilities recognized	(358)	(338)
Postretirement Health Benefit Plan
Amounts recognized in the consolidated balance sheets
Current portion of pension and postretirement liabilities	(707)	(676)
Pension and postretirement liabilities, less current portion	(12,961)	(11,858)
Liabilities recognized	$ (13,668)	$ (12,534)

EMPLOYEE BENEFIT PLANS - Compon

EMPLOYEE BENEFIT PLANS - Components of Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Components of net periodic benefit cost (credit)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income	Other, net	Other, net	Other, net
Pension settlement expense	$ 0	$ 0	$ 0
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income	Other, net	Other, net	Other, net
Noncash charge to pension settlement expense	$ 0	$ 0	$ 0
Supplemental Benefit Plan
Components of net periodic benefit cost (credit)
Interest cost	16	7	4
Amortization of net actuarial (gain) loss	(4)	8	9
Net periodic benefit cost (credit)	12	15	13
Postretirement Health Benefit Plan
Components of net periodic benefit cost (credit)
Service cost	78	156	192
Interest cost	599	441	427
Amortization of net actuarial (gain) loss	(1,326)	(765)	(548)
Net periodic benefit cost (credit)	$ (649)	$ (168)	$ 71

EMPLOYEE BENEFIT PLANS - Includ

EMPLOYEE BENEFIT PLANS - Included in AOCI (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Supplemental Benefit Plan
Pre-tax amounts included in accumulated other comprehensive loss that have not yet been recognized in net periodic benefit cost
Unrecognized net actuarial gain	$ (9)	$ (18)
Postretirement Health Benefit Plan
Pre-tax amounts included in accumulated other comprehensive loss that have not yet been recognized in net periodic benefit cost
Unrecognized net actuarial gain	$ (6,806)	$ (9,269)

EMPLOYEE BENEFIT PLANS - Discou

EMPLOYEE BENEFIT PLANS - Discount rate and assumptions (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Supplemental Benefit Plan
Weighted-average assumptions used to determine nonunion benefit obligations
Discount rate (as a percent)	4.30%	4.60%
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	4.60%	1.80%	1.10%
Postretirement Health Benefit Plan
Weighted-average assumptions used to determine nonunion benefit obligations
Discount rate (as a percent)	4.80%	5%
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	5%	2.70%	2.30%

EMPLOYEE BENEFIT PLANS - Health

EMPLOYEE BENEFIT PLANS - Health care trend rates (Details) - Postretirement Health Benefit Plan	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Assumed health care cost trend rates
Health care cost trend rate assumed for next year (as a percent)	7%	7%
Rate to which the cost trend rate is assumed to decline (as a percent)	4.50%	4.50%
Year that the rate reaches the cost trend assumed rate	2035	2034

EMPLOYEE BENEFIT PLANS - Future

EMPLOYEE BENEFIT PLANS - Future benefit payments (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Supplemental Benefit Plan
Estimated future benefit payments
2028	$ 424
Postretirement Health Benefit Plan
Estimated future benefit payments
2024	707
2025	744
2026	747
2027	754
2028	761
2029-2033	$ 3,836

EMPLOYEE BENEFIT PLANS - Deferr

EMPLOYEE BENEFIT PLANS - Deferred Comp Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Deferred salary agreements
Deferred Compensation Plans
Recorded liabilities	$ 1.1	$ 1.3
Voluntary Savings Plan - mutual funds held in trust
Deferred Compensation Plans
Minimum period for election to defer receipt of a portion of salary and incentive compensation	6 months
Voluntary Savings Plan - mutual funds held in trust | Other long-term assets
Deferred Compensation Plans
VSP assets	$ 4.6	4
Voluntary Savings Plan - mutual funds held in trust | Other long-term liabilities
Deferred Compensation Plans
VSP liabilities	$ 4.6	$ 4

EMPLOYEE BENEFIT PLANS - Define

EMPLOYEE BENEFIT PLANS - Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash Long-Term Incentive Compensation Plan
Earning period of Long-term cash incentive plan	3 years
Incentive payments accrued for Long-Term Cash Incentive Plan	$ 26.3	$ 29.5	$ 28.3
Other Plans
Cash surrender value of life insurance policies	48.5	54.7
Recognized (losses) gains associated with changes in the cash surrender value and proceeds from life insurance policies	$ 4.6	(2.7)	4.1
401(k) Plan
Defined Contribution Plans
Maximum percentage of salary permitted to be deferred by plan participants	69%
Rate of employer match on participant contributions	50%
Maximum percentage of participants compensation that is eligible for 50% matching contribution	6%
Expense for employer contribution to defined contribution plan	$ 7.1	9.4	7.7
Defined Contribution Plan
Defined Contribution Plans
Expense for employer contribution to defined contribution plan	$ 13.1	$ 19.1	$ 16.8
Period of service for participants' full vesting in the employer's contributions	3 years

EMPLOYEE BENEFIT PLANS - Multie

EMPLOYEE BENEFIT PLANS - Multiemployer Plans (Details) - Asset Based $ in Thousands				3 Months Ended		12 Months Ended
	Aug. 01, 2023	Aug. 01, 2022	Aug. 01, 2021	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2023 USD ($) plan	Jan. 31, 2023	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jan. 01, 2023	Jan. 01, 2022	Jan. 01, 2021
Multiemployer Plans
Minimum funded percentage of plans in green zone						80%
Pension Plans
Multiemployer Plans
Number of multiemployer plans to which ABF Freight currently contributes | plan						25
Maximum funded percentage of plans in yellow zone						80%
Maximum funded percentage of plans in red zone						65%
Maximum projected time to insolvency for plans in "critical and declining" status						14 years
Maximum projected time to insolvency for plans in "critical and declining" status if additional criteria apply						19 years
Threshold ratio of inactive to active participants for greater insolvency period to determine "critical and declining" status						2
Threshold funded percentage for greater insolvency period to determine "critical and declining" status						80%
Percentage of contributions to the multiemployer pension plans that are in critical and declining status						6%
Percentage of contributions to the multiemployer pension plans that are in critical status						53%
Percentage of contributions to the multiemployer pension plans that are in endangered status						0%
Total multiemployer pension contributions paid						$ 162,484		$ 154,558	$ 146,893
Pension Plans | Central States, Southeast and Southwest Areas Pension Plan
Multiemployer Plans
Multiemployer pension contributions paid, individually significant						$ 77,708		$ 75,306	$ 71,045
Threshold percentage of the entity's contributions relative to total fund contributions, which was exceeded during the period								5%	5%
Percentage of contributions to multiemployer pension plan						50%		50%	50%
Actuarially certified projected funded percentage of multiemployer pension plan										97.50%	14.50%	17.10%
Pension Plans | Western Conference Of Teamsters Pension Plan
Multiemployer Plans
Multiemployer pension contributions paid, individually significant						$ 29,540		$ 28,051	$ 25,861
Pension Plans | Central Pennsylvania Teamsters Defined Benefit Plan(
Multiemployer Plans
Multiemployer pension contributions paid, individually significant						15,540		14,421	13,931
Pension Plans | I. B. of T. Union Local No. 710 Pension Fund
Multiemployer Plans
Multiemployer pension contributions paid, individually significant						10,676		9,838	9,553
Threshold percentage of the entity's contributions relative to total fund contributions, which was exceeded during the period							5%
Pension Plans | New England Teamsters Pension Fund
Multiemployer Plans
Multiemployer pension contributions paid, individually significant						4,636		4,449	4,357
Contributions to multiemployer plans related to pension fund withdrawal liability						1,600		1,600	1,600
Multiemployer pension fund withdrawal liability charge (pre-tax)					$ 37,900
Initial lump sum payment of withdrawal liability				$ 15,100
Withdrawal liability monthly payments period (in years)				18 years
Pension Plans | All other plans in the aggregate
Multiemployer Plans
Multiemployer pension contributions paid, individually insignificant						$ 24,384		22,493	22,146
Pension Plans | Multiemployer pension plans receiving 1% to 2% ABF Freight's total multiemployer pension contributions | Minimum
Multiemployer Plans
Percentage of contributions to each individually insignificant multiemployer pension plan						1%
Pension Plans | Multiemployer pension plans receiving 1% to 2% ABF Freight's total multiemployer pension contributions | Maximum
Multiemployer Plans
Percentage of contributions to each individually insignificant multiemployer pension plan						2%
Health And Welfare Plans
Multiemployer Plans
Number of multiemployer plans to which ABF Freight currently contributes | plan						38
Total multiemployer pension contributions paid						$ 215,600		$ 194,400	$ 176,200
Percentage increase in contribution rate for time worked related to benefit costs	5.70%	4.30%	4.30%

STOCKHOLDERS' EQUITY - AOCI Com

STOCKHOLDERS' EQUITY - AOCI Components (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income
Total after-tax amount	$ 1,242,363	$ 1,151,401	$ 929,067	$ 828,593
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income
Total pre-tax amount	5,817	9,566	4,977
Total after-tax amount	4,324	7,103	3,699	$ 1,190
Unrecognized Net Periodic Benefit Credit
Accumulated Other Comprehensive Income
Total pre-tax amount	6,816	9,287	5,602
Total after-tax amount	5,061	6,896	4,160
Interest Rate Swap
Accumulated Other Comprehensive Income
Total pre-tax amount	1,710	3,526	419
Total after-tax amount	1,263	2,604	309
Foreign Currency Translation
Accumulated Other Comprehensive Income
Total pre-tax amount	(2,709)	(3,247)	(1,044)
Total after-tax amount	$ (2,000)	$ (2,397)	$ (770)

STOCKHOLDERS' EQUITY - AOCI Cha

STOCKHOLDERS' EQUITY - AOCI Changes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Changes in accumulated other comprehensive income, net of tax, by component
Balances	$ 1,151,401	$ 929,067	$ 828,593
OTHER COMPREHENSIVE INCOME (LOSS), net of tax	(2,779)	3,404	2,509
Balances	1,242,363	1,151,401	929,067
Accumulated Other Comprehensive Income
Changes in accumulated other comprehensive income, net of tax, by component
Balances	7,103	3,699	1,190
Other comprehensive income (loss) before reclassifications	(1,791)	3,966
Amounts reclassified from accumulated other comprehensive income	(988)	(562)
OTHER COMPREHENSIVE INCOME (LOSS), net of tax	(2,779)	3,404	2,509
Balances	4,324	7,103	3,699
Unrecognized Net Periodic Benefit Credit
Changes in accumulated other comprehensive income, net of tax, by component
Balances	6,896	4,160
Other comprehensive income (loss) before reclassifications	(847)	3,298
Amounts reclassified from accumulated other comprehensive income	(988)	(562)
OTHER COMPREHENSIVE INCOME (LOSS), net of tax	(1,835)	2,736
Balances	5,061	6,896	4,160
Interest Rate Swap
Changes in accumulated other comprehensive income, net of tax, by component
Balances	2,604	309
Other comprehensive income (loss) before reclassifications	(1,341)	2,295
OTHER COMPREHENSIVE INCOME (LOSS), net of tax	(1,341)	2,295
Balances	1,263	2,604	309
Foreign Currency Translation
Changes in accumulated other comprehensive income, net of tax, by component
Balances	(2,397)	(770)
Other comprehensive income (loss) before reclassifications	397	(1,627)
OTHER COMPREHENSIVE INCOME (LOSS), net of tax	397	(1,627)
Balances	$ (2,000)	$ (2,397)	$ (770)

STOCKHOLDERS' EQUITY - Reclass

STOCKHOLDERS' EQUITY - Reclass (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Unrecognized Net Periodic Benefit Credit
Significant reclassifications out of accumulated other comprehensive loss by component
Tax expense	$ (342)	$ (195)
Total, net of tax	988	562
Amortization of net actuarial gain
Significant reclassifications out of accumulated other comprehensive loss by component
Total, pre-tax	$ 1,330	$ 757

STOCKHOLDERS' EQUITY - Dividend

STOCKHOLDERS' EQUITY - Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Feb. 02, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Dividends on Common Stock
Dividends declared (in dollars per share)		$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.08
Dividend Amount		$ 2,846	$ 2,887	$ 2,894	$ 2,915	$ 2,938	$ 2,965	$ 2,949	$ 1,978	$ 11,542	$ 10,830	$ 8,139
Subsequent Event
Dividends on Common Stock
Dividends declared (in dollars per share)	$ 0.12

STOCKHOLDERS' EQUITY - Treasury

STOCKHOLDERS' EQUITY - Treasury Stock Activity (Details) - USD ($) $ in Thousands	2 Months Ended	12 Months Ended
	Feb. 19, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Feb. 23, 2024	Feb. 28, 2023
Treasury Stock
Cost of repurchased shares		$ 91,531	$ 65,002	$ 83,100
Purchases of treasury stock		$ (91,531)	$ (65,002)	(83,100)
Forward contract for accelerated share repurchase				$ (25,000)
Treasury stock, at cost, shares		6,460,137	5,529,383
Stock Repurchase Program
Treasury Stock
Amount of stock repurchases authorized						$ 125,000
Number of shares repurchased during the period		930,754
Cost of repurchased shares		$ 91,500
Amount available for repurchase		$ 33,500
Stock Repurchase Program | Subsequent Event
Treasury Stock
Amount of stock repurchases authorized					$ 125,000
Number of shares repurchased during the period	51,220
Cost of repurchased shares	$ 6,100
Stock Repurchase Program, 10b5-1 Plans
Treasury Stock
Number of shares repurchased during the period		501,146
Cost of repurchased shares		$ 47,600

SHARE-BASED COMPENSATION (Detai

SHARE-BASED COMPENSATION (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based compensation
Number of shares authorized	4,900,000
Restricted Stock Units
Award activity
Outstanding at the beginning of the period (in shares)	1,023,251
Granted (in shares)	149,350	164,739	136,295
Vested (in shares)	(381,724)
Forfeited (in shares)	(65,444)
Outstanding at the end of the period (in shares)	725,433	1,023,251
Weighted-Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 38.83
Granted (in dollars per share)	86.53	$ 78.57	$ 86.96
Vested (in dollars per share)	36.04
Forfeited (in dollars per share)	51.97
Outstanding at the end of the period (in dollars per share)	$ 48.94	$ 38.83
Other disclosure
Fair value of restricted stock awards vested	$ 34.2	$ 48.1	$ 36.4
Unrecognized compensation cost	$ 14
Weighted-average period of recognition of unrecognized compensation cost	10 months 24 days

EARNINGS PER SHARE - Basic And

EARNINGS PER SHARE - Basic And Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Basic, numerator:
Net income from continuing operations	$ 142,164	$ 294,648	$ 210,459
Net income from discontinued operations	53,269	3,561	3,062
Net income	$ 195,433	$ 298,209	$ 213,521
Basic, denominator:
Weighted-average shares	24,018,801	24,585,205	25,471,939
Basic earnings per common share
Continuing operations (in dollars per share)	$ 5.92	$ 11.98	$ 8.26
Discontinued operations (in dollars per share)	2.22	0.14	0.12
BASIC EARNINGS PER COMMON SHARE (in dollars per share)	$ 8.14	$ 12.13	$ 8.38
Diluted, numerator:
Net income from continuing operations	$ 142,164	$ 294,648	$ 210,459
Net income from discontinued operations	53,269	3,561	3,062
Net income	$ 195,433	$ 298,209	$ 213,521
Diluted, denominator:
Weighted-average shares	24,018,801	24,585,205	25,471,939
Effect of dilutive securities	615,816	919,303	1,300,187
Adjusted weighted-average shares and assumed conversions	24,634,617	25,504,508	26,772,126
Diluted earnings per common share
Continuing operations (in dollars per share)	$ 5.77	$ 11.55	$ 7.86
Discontinued operations (in dollars per share)	2.16	0.14	0.11
DILUTED EARNINGS PER COMMON SHARE (in dollars per share)	$ 7.93	$ 11.69	$ 7.98

OPERATING SEGMENT DATA - Revenu

OPERATING SEGMENT DATA - Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
REVENUES
Revenues	$ 4,427,443	$ 5,029,008	$ 3,766,185
Asset Based
REVENUES
Revenues	2,749,803	2,896,284	2,470,529
Asset-Light
REVENUES
Revenues	1,673,399	2,128,394	1,291,679
Operating Segments | Asset Based
REVENUES
Revenues	2,871,004	3,010,900	2,573,773
Operating Segments | Asset-Light
REVENUES
Revenues	1,680,645	2,139,272	1,300,626
Other and eliminations
REVENUES
Revenues	$ (124,206)	$ (121,164)	$ (108,214)

OPERATING SEGMENT DATA - Operat

OPERATING SEGMENT DATA - Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING EXPENSES
Salaries, wages, and benefits			$ 1,781,304	$ 1,728,653	$ 1,527,533
Fuel, supplies, and expenses			479,688	488,009	360,657
Depreciation and amortization			145,349	138,159	122,560
Contingent consideration			(19,100)	18,300
Lease impairment charges	$ 30,200		30,162
Gain on sale of subsidiary				(402)	(6,923)
Other			194,752	160,698	129,351
Total consolidated operating expenses			4,254,824	4,634,482	3,489,207
Gain on sale of property and equipment			(4,797)	11,650	8,520
Increase in fair value of equity investment		$ 3,700	3,739
Operating Segments | Asset Based
OPERATING EXPENSES
Salaries, wages, and benefits			1,379,756	1,293,487	1,198,253
Fuel, supplies, and expenses			361,355	378,558	266,139
Operating taxes and licenses			55,918	52,290	49,461
Insurance			52,025	47,382	37,800
Communications and utilities			19,288	18,949	18,773
Depreciation and amortization			104,165	97,322	93,799
Rents and purchased transportation			338,575	441,167	364,345
Shared services			279,248	281,698	263,532
(Gain) loss on sale of property and equipment and lease impairment charges			982	(12,468)	(8,676)
Lease impairment charges			700
Innovative technology costs			21,711	27,207	27,631
Other			4,829	4,175	2,009
Total consolidated operating expenses			2,617,852	2,629,767	2,313,066
Noncash gain on a like-kind property exchange of a service center				(4,300)
Operating Segments | Asset Based | Land and structures
OPERATING EXPENSES
Gain on sale of property and equipment					8,600
Operating Segments | Asset-Light
OPERATING EXPENSES
Purchased transportation			1,435,604	1,784,668	1,097,332
Supplies and expenses			12,094	13,955	8,661
Depreciation and amortization			20,370	20,730	11,387
Shared services			194,296	218,133	132,137
Contingent consideration			(19,100)	18,300
Lease impairment charges			14,407
Legal settlement			9,500
Gain on sale of subsidiary				(402)	(6,923)
Other			25,745	31,163	11,635
Total consolidated operating expenses			1,692,916	2,086,547	1,254,229
Other and eliminations
OPERATING EXPENSES
Depreciation and amortization			20,814	20,107	17,374
Lease impairment charges			15,100
Total consolidated operating expenses			$ (55,944)	$ (81,832)	$ (78,088)

OPERATING SEGMENT DATA - Oper_2

OPERATING SEGMENT DATA - Operating Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING INCOME (LOSS)
Operating income	$ 172,619	$ 394,526	$ 276,978
OTHER INCOME (COSTS)
Interest and dividend income	14,728	3,873	1,226
Interest and other related financing costs	(9,094)	(7,726)	(8,914)
Other, net	8,662	(2,370)	3,797
TOTAL OTHER INCOME (COSTS)	14,296	(6,223)	(3,891)
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	186,915	388,303	273,087
Operating Segments | Asset Based
OPERATING INCOME (LOSS)
Operating income	253,152	381,133	260,707
Operating Segments | Asset-Light
OPERATING INCOME (LOSS)
Operating income	(12,271)	52,725	46,397
Other and eliminations
OPERATING INCOME (LOSS)
Operating income	$ (68,262)	$ (39,332)	$ (30,126)

OPERATING SEGMENT DATA - Reve_2

OPERATING SEGMENT DATA - Revenue from Customers (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
REVENUES
Revenues	$ 4,427,443	$ 5,029,008	$ 3,766,185
Asset Based
REVENUES
Revenues	2,749,803	2,896,284	2,470,529
Asset-Light
REVENUES
Revenues	1,673,399	2,128,394	1,291,679
Corporate and other
REVENUES
Revenues	4,241	4,330	3,977
Operating Segments | Asset Based
REVENUES
Revenues	2,871,004	3,010,900	2,573,773
Operating Segments | Asset-Light
REVENUES
Revenues	1,680,645	2,139,272	1,300,626
Intersegment revenues
REVENUES
Revenues	(128,447)	(125,494)	(112,191)
Intersegment revenues | Asset Based
REVENUES
Revenues	121,201	114,616	103,244
Intersegment revenues | Asset-Light
REVENUES
Revenues	7,246	10,878	8,947
Other and eliminations
REVENUES
Revenues	$ (124,206)	$ (121,164)	$ (108,214)

OPERATING SEGMENT DATA - Capita

OPERATING SEGMENT DATA - Capital expenditures, depreciation and amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	$ 252,411	$ 229,209	$ 116,938
DEPRECIATION AND AMORTIZATION EXPENSE	145,349	138,159	122,560
Amortization of intangibles	12,829	12,920	5,357
Research and development costs	52,400	40,800
Other and eliminations
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	37,752	77,720	11,193
DEPRECIATION AND AMORTIZATION EXPENSE	20,814	20,107	17,374
Assets acquired through notes payable		3,400
Other and eliminations | Service center
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS		37,500
Asset Based | Operating Segments
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	207,072	137,117	96,180
DEPRECIATION AND AMORTIZATION EXPENSE	104,165	97,322	93,799
Assets acquired through notes payable	33,500	79,000	59,700
Asset-Light | Operating Segments
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	7,587	14,372	9,565
DEPRECIATION AND AMORTIZATION EXPENSE	20,370	20,730	11,387
Amortization of intangibles	$ 12,800	$ 12,900	$ 5,300

OPERATING SEGMENT DATA - Oper_3

OPERATING SEGMENT DATA - Operating Expenses by Category (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING EXPENSES
Salaries, wages, and benefits		$ 1,781,304	$ 1,728,653	$ 1,527,533
Rents, purchased transportation, and other costs of services		1,642,669	2,100,663	1,349,106
Fuel, supplies, and expenses		479,688	488,009	360,657
Depreciation and amortization		145,349	138,159	122,560
Contingent consideration		(19,100)	18,300
Lease impairment charges	$ 30,200	30,162
Other		194,752	160,698	129,351
Total consolidated operating expenses		4,254,824	4,634,482	3,489,207
Gain on sale of subsidiaries			402	6,923
Gain on sale of property and equipment		(4,797)	11,650	8,520
Innovative technology costs		52,400	40,800	32,800
Operating Segments | Asset Based
OPERATING EXPENSES
Salaries, wages, and benefits		1,379,756	1,293,487	1,198,253
Fuel, supplies, and expenses		361,355	378,558	266,139
Depreciation and amortization		104,165	97,322	93,799
Lease impairment charges		700
Other		4,829	4,175	2,009
Total consolidated operating expenses		2,617,852	2,629,767	2,313,066
Gain related to sale of property and equipment and sale of replaced equipment and like-kind exchange of service center property			12,500
Operating Segments | Asset Based | Land and structures
OPERATING EXPENSES
Gain on sale of property and equipment				8,600
Operating Segments | Asset-Light
OPERATING EXPENSES
Depreciation and amortization		20,370	20,730	11,387
Contingent consideration		(19,100)	18,300
Lease impairment charges		14,407
Other		25,745	31,163	11,635
Total consolidated operating expenses		1,692,916	2,086,547	1,254,229
Estimated settlement expense		9,500
Gain on sale of subsidiaries			402	6,923
Other and eliminations
OPERATING EXPENSES
Depreciation and amortization		20,814	20,107	17,374
Lease impairment charges		15,100
Total consolidated operating expenses		$ (55,944)	$ (81,832)	$ (78,088)

LEGAL PROCEEDINGS, ENVIRONMEN_2

LEGAL PROCEEDINGS, ENVIRONMENTAL MATTERS, AND OTHER EVENTS (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Sep. 30, 2023
Compliance issues under federal Clean Water Act
Environmental Matters and Other Events
Amount paid for civil penalties		$ 0.5
Claim related to employee classification under Fair Labor Standards Act | Asset-Light
Environmental Matters and Other Events
Estimated settlement expense	$ 9.5

SCHEDULE II - VALUATION AND Q_2

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for doubtful accounts receivable and revenue adjustments
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	$ 13,892	$ 13,016	$ 7,693
Additions, Charged to Costs and Expenses	3,633	6,852	1,334
Additions, Charged to Other Accounts	3,512	2,761	7,783
Deductions	10,691	8,737	3,794
Balance at End of Period	10,346	13,892	13,016
Allowance for other accounts receivable
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	713	690	660
Additions, Charged to Costs and Expenses	18	23	30
Balance at End of Period	731	713	690
Allowance for deferred tax assets
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	1,707	2,196	1,284
Deductions	(44)	489	(912)
Balance at End of Period	$ 1,751	$ 1,707	$ 2,196

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ 195,433	$ 298,209	$ 213,521

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	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