ArcBest (ARCB) 10-K 25 Feb 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 25, 2022	Jun. 30, 2021
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
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	No
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
Entity Shell Company	false
Entity Public Float			$ 1,458,553,375
Entity Common Stock, Shares Outstanding		24,597,758
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	2021
Document Fiscal Period Focus	FY
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
CURRENT ASSETS
Cash and cash equivalents	$ 76,620	$ 303,954
Short-term investments	48,339	65,408
Accounts receivable, less allowances (2021 - $13,226; 2020 - $7,851)	582,344	320,870
Other accounts receivable, less allowances (2021 - $690; 2020 - $660)	13,094	14,343
Prepaid expenses	40,104	37,774
Prepaid and refundable income taxes	9,654	11,397
Other	5,898	4,422
TOTAL CURRENT ASSETS	776,053	758,168
PROPERTY, PLANT AND EQUIPMENT
Land and structures	350,694	342,178
Revenue equipment	980,283	916,760
Service, office, and other equipment	251,085	233,810
Software	175,989	163,193
Leasehold improvements	16,931	15,156
TOTAL PROPERTY, PLANT AND EQUIPMENT, Gross	1,774,982	1,671,097
Less allowances for depreciation and amortization	1,079,061	992,407
PROPERTY, PLANT AND EQUIPMENT, net	695,921	678,690
GOODWILL	300,337	88,320
INTANGIBLE ASSETS, net	126,580	54,981
OPERATING RIGHT-OF-USE ASSETS	106,686	115,195
DEFERRED INCOME TAXES	5,470	6,158
OTHER LONG-TERM ASSETS	101,629	77,496
TOTAL ASSETS	2,112,676	1,779,008
CURRENT LIABILITIES
Accounts payable	311,401	170,898
Income taxes payable	12,087	316
Accrued expenses	305,851	246,746
Current portion of long-term debt	50,615	67,105
Current portion of operating lease liabilities	22,740	21,482
TOTAL CURRENT LIABILITIES	702,694	506,547
LONG-TERM DEBT, less current portion	174,917	217,119
OPERATING LEASE LIABILITIES, less current portion	88,835	97,839
POSTRETIREMENT LIABILITIES, less current portion	16,733	18,555
OTHER LONG-TERM LIABILITIES	135,537	37,948
DEFERRED INCOME TAXES	64,893	72,407
STOCKHOLDERS' EQUITY
Common stock, $0.01 par value, authorized 70,000,000 shares; issued 2021: 29,359,597 shares, 2020: 29,045,309 shares	294	290
Additional paid-in capital	318,033	342,354
Retained earnings	801,314	595,932
Treasury stock, at cost, 2021: 4,492,514 shares; 2020: 3,656,938 shares	(194,273)	(111,173)
Accumulated other comprehensive income	3,699	1,190
TOTAL STOCKHOLDERS' EQUITY	929,067	828,593
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 2,112,676	$ 1,779,008

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
CONSOLIDATED BALANCE SHEETS
Accounts receivable, allowances (in dollars)	$ 13,226	$ 7,851
Other accounts receivable, allowances (in dollars)	$ 690	$ 660
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	29,359,597	29,045,309
Treasury stock, at cost, shares	4,492,514	3,656,938

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED STATEMENTS OF OPERATIONS
REVENUES									$ 3,980,067	$ 2,940,163	$ 2,988,310
OPERATING EXPENSES									3,699,081	2,841,885	2,924,540
OPERATING INCOME									280,986	98,278	63,770
OTHER INCOME (COSTS)
Interest and dividend income									1,275	3,616	6,453
Interest and other related financing costs									(8,904)	(11,697)	(11,467)
Other, net									3,797	2,299	(7,285)
Total other costs									(3,832)	(5,782)	(12,299)
INCOME BEFORE INCOME TAXES									277,154	92,496	51,471
INCOME TAX PROVISION									63,633	21,396	11,486
NET INCOME									$ 213,521	$ 71,100	$ 39,985
EARNINGS PER COMMON SHARE
Basic									$ 8.38	$ 2.80	$ 1.56
Diluted									$ 7.98	$ 2.69	$ 1.51
AVERAGE COMMON SHARES OUTSTANDING
Basic									25,471,939	25,410,232	25,535,529
Diluted									26,772,126	26,422,523	26,450,055
CASH DIVIDENDS DECLARED PER COMMON SHARE	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.32	$ 0.32	$ 0.32

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
NET INCOME	$ 213,521	$ 71,100	$ 39,985
Postretirement benefit plans:
Net actuarial gain, net of tax of: (2021 - $451; 2020 - $513, 2019 - $2,308)	1,300	1,480	6,657
Pension settlement expense, including termination expense, net of tax of: (2021 - $-; 2020 - $23, 2019 - $1,167)		66	7,338
Amortization of unrecognized net periodic benefit cost (credit), net of tax of: (2021 - $139; 2020 - $152, 2019 - $314)
Net actuarial (gain) loss	(400)	(437)	931
Prior service credit		(1)	(25)
Interest rate swap and foreign currency translation:
Change in unrealized income (loss) on interest rate swap, net of tax of: (2021 - $534; 2020 - $277, 2019 - $357)	1,507	(782)	(1,007)
Change in foreign currency translation, net of tax of: (2021 - $36; 2020 - $232, 2019 - $194)	102	661	547
OTHER COMPREHENSIVE INCOME, net of tax	2,509	987	14,441
TOTAL COMPREHENSIVE INCOME	$ 216,030	$ 72,087	$ 54,426

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net actuarial loss, tax (benefit)	$ 451	$ 513	$ 2,308
Pension settlement expense, tax		23	1,167
Amortization of unrecognized net periodic benefit credit, tax	(139)	(152)	314
Change in unrealized gain (loss) on interest rate swap, tax (benefit)	534	(277)	(357)
Change in foreign currency translation, tax expense (benefit)	$ 36	$ 232	$ 194

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common StockCumulative Effect, Period of Adoption, Adjusted Balance	Common Stock	Additional Paid-In CapitalCumulative Effect, Period of Adoption, Adjusted Balance	Additional Paid-In Capital	Retained EarningsCumulative Effect, Period of Adoption, Adjustment	Retained EarningsCumulative Effect, Period of Adoption, Adjusted Balance	Retained Earnings	Treasury StockCumulative Effect, Period of Adoption, Adjusted Balance	Treasury Stock	Accumulated Other Comprehensive Income (Loss)Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Other Comprehensive Income (Loss)	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjusted Balance	Total
Balances at Dec. 31, 2018		$ 287		$ 325,712			$ 501,389		$ (95,468)		$ (14,238)			$ 717,682
Balances (in shares) at Dec. 31, 2018		28,685							3,098
Increase (Decrease) in Stockholders' Equity
Net income							39,985							39,985
Other comprehensive income, net of tax											14,441			14,441
Issuance of common stock under share-based compensation plans		$ 1		(1)
Issuance of common stock under share-based compensation plans (in shares)		126
Shares withheld for employee tax remittance on share-based compensation				(1,291)										(1,291)
Share-based compensation expense				9,523										9,523
Purchase of treasury stock									$ (9,110)					(9,110)
Purchase of treasury stock (in shares)									307
Dividends declared on common stock							(8,187)							(8,187)
Balances at Dec. 31, 2019	$ 288	$ 288	$ 333,943	333,943	$ (198)	$ 532,989	533,187	$ (104,578)	$ (104,578)	$ 203	203	$ (198)	$ 762,845	763,043
Balances (in shares) at Dec. 31, 2019	28,811	28,811						3,405	3,405
Increase (Decrease) in Stockholders' Equity
Net income							71,100							71,100
Other comprehensive income, net of tax											987			987
Issuance of common stock under share-based compensation plans		$ 2		(2)
Issuance of common stock under share-based compensation plans (in shares)		234
Shares withheld for employee tax remittance on share-based compensation				(2,065)										(2,065)
Share-based compensation expense				10,478										10,478
Purchase of treasury stock									$ (6,595)					(6,595)
Purchase of treasury stock (in shares)									252
Dividends declared on common stock							(8,157)							(8,157)
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							3,657
Increase (Decrease) in Stockholders' Equity
Net income							213,521							213,521
Other comprehensive income, 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
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
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							4,493

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES
Net income	$ 213,521	$ 71,100	$ 39,985
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	118,864	114,379	108,099
Amortization of intangibles	5,357	4,012	4,367
Pension settlement expense		89	8,505
Share-based compensation expense	11,426	10,478	9,523
Provision for losses on accounts receivable	1,466	4,327	1,223
Change in deferred income taxes	(7,589)	7,715	5,411
Asset impairment			26,514
Gain on sale of property and equipment and lease termination	(8,520)	(2,376)	(5,247)
Gain on sale of subsidiaries	(6,923)
Changes in operating assets and liabilities:
Receivables	(122,782)	(38,129)	13,720
Prepaid expenses	(1,482)	(7,966)	(4,756)
Other assets	354	2,646	(1,365)
Income taxes	13,136	(1,712)	(8,720)
Operating right-of-use assets and lease liabilities, net	623	756	728
Accounts payable, accrued expenses, and other liabilities	106,064	40,670	(27,623)
NET CASH PROVIDED BY OPERATING ACTIVITIES	323,515	205,989	170,364
INVESTING ACTIVITIES
Purchases of property, plant and equipment, net of financings	(58,412)	(43,248)	(90,955)
Proceeds from sale of property and equipment	13,815	13,348	13,490
Business acquisitions, net of cash acquired	(239,380)
Proceeds from sale of subsidiaries	9,013
Purchases of short-term investments	(56,011)	(165,133)	(129,709)
Proceeds from sale of short-term investments	73,182	216,735	120,409
Purchase of long-term investments	(25,350)
Capitalization of internally developed software	(20,061)	(14,241)	(11,476)
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	(303,204)	7,461	(98,241)
FINANCING ACTIVITIES
Borrowings under credit facilities	50,000	180,000
Borrowings under accounts receivable securitization program		45,000
Proceeds from notes payable	3,523		20,410
Payments on long-term debt	(171,915)	(326,098)	(58,938)
Net change in book overdrafts	(1,957)	6,510	(2,722)
Deferred financing costs	(314)		(562)
Payment of common stock dividends	(8,139)	(8,157)	(8,187)
Purchases of treasury stock	(83,100)	(6,595)	(9,110)
Forward contract for accelerated share repurchase	(25,000)
Payments for tax withheld on share-based compensation	(10,743)	(2,065)	(1,291)
NET CASH USED IN FINANCING ACTIVITIES	(247,645)	(111,405)	(60,400)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(227,334)	102,045	11,723
Cash and cash equivalents at beginning of period	303,954	201,909	190,186
CASH AND CASH EQUIVALENTS AT END OF PERIOD	76,620	303,954	201,909
NONCASH INVESTING ACTIVITIES
Equipment and other financings	59,700	61,803	70,372
Accruals for equipment received	1,704	1,667	234
Lease liabilities arising from obtaining right-of-use assets	$ 14,671	$ 67,819	$ 32,761

ORGANIZATION AND DESCRIPTION OF

ORGANIZATION AND DESCRIPTION OF THE BUSINESS AND FINANCIAL STATEMENT PRESENTATION	12 Months Ended
	Dec. 31, 2021
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 62% of the Company’s 2021 total revenues before other revenues and intercompany eliminations. As of December 2021, approximately 82% of the Asset-Based segment’s employees were covered under a collective bargaining agreement, the ABF National Master Freight Agreement (the “2018 ABF NMFA”), with the International Brotherhood of Teamsters (the “IBT”) which will remain in effect through June 30, 2023. ​ Financial Statement Presentation ​ Consolidation: ​ Segment Information: ​ Use of Estimates: ​ ​ ​

ACCOUNTING POLICIES

ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2021
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 earnings. ​ 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 4% of its revenues in 2021, 2020, or 2019 or more than 7% of its accounts receivable balance at December 31, 2021 and 2020. The Company performs ongoing credit evaluations of its customers and generally does not require collateral. Historically, credit losses have been within management’s expectations. ​ Allowances: ​ Property, Plant and Equipment, Including Repairs and Maintenance: Purchases of property, plant and equipment are recorded at cost. For financial reporting purposes, property, plant and equipment is depreciated principally by the straight-line method, using the following useful lives: structures – primarily 15 to 60 years ; revenue equipment – 3 to 16 years ; and other equipment – 2 to 15 years . The Company utilizes tractors and trailers in its operations. Tractors and trailers are commonly referred to as “revenue equipment” in the transportation business. The Company periodically reviews and adjusts, as appropriate, the residual values and useful lives of revenue equipment and other equipment. For tax reporting purposes, accelerated depreciation or cost recovery methods are used. Gains and losses on asset sales are reflected in the year of disposal. Exchanges of nonmonetary assets that have commercial substance are measured based on the fair value of the assets exchanged. Tires purchased with revenue equipment are capitalized as a part of the cost of such equipment, with replacement tires being expensed when placed in service. Repair and maintenance costs associated with property, plant and equipment are expensed as incurred if the costs do not extend the useful life of the asset. If such costs do extend the useful life of the asset, the costs are capitalized and depreciated over the appropriate remaining useful life. ​ Computer Software for Internal Use, Including Web Site Development and Cloud Computing Costs: The Company capitalizes the costs of software acquired from third parties and qualifying internal computer software costs incurred during the application development stage, or during the implementation stage for cloud computing or hosting arrangements. Costs incurred in the preliminary project stage and postimplementation-operation stage, which includes maintenance and training costs, are expensed as incurred. For financial reporting purposes, capitalized software costs are amortized by the 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 $0.6 million and $1.1 million are reported within other noncurrent assets as of December 31, 2021 and 2020, respectively. ​ Business Combinations: ​ On November 1, 2021, the Company acquired MoLo Solutions, LLC (“MoLo”), a Chicago-based truckload freight brokerage company. Terms of the transaction included initial consideration paid at closing of $239.4 million, subject to certain post-closing adjustments which were estimated at closing and will be finalized post-closing, and the potential for additional cash consideration based on achievement of certain targets of adjusted earnings before interest, taxes, depreciation, and amortization as adjusted for certain items pursuant to the merger agreement for years 2023 through 2025 (see Note D). ​ 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 assesses qualitative factors to determine if it is more likely than not that the fair value of indefinite-lived intangible assets is less than its carrying value and performs a quantitative analysis 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. ​ 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. ​ Nonunion Defined Benefit Pension, Supplemental Benefit, and Postretirement Health Benefit Plans: ​ The Company recognizes the funded status of the supplemental benefit plan (the “SBP”) and postretirement health benefit plan in the consolidated balance sheet and recognizes changes in the funded status, net of tax, in the year in which they occur as a component of other comprehensive income or loss. The benefit obligations of the SBP and postretirement health benefit plan represent the funded status, as these plans do not have plan assets. Amounts recognized in other comprehensive income or loss are subsequently expensed as components of net periodic benefit cost by amortizing unrecognized net actuarial losses over the average remaining 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 nonunion defined benefit pension plan or the SBP since the accrual of benefits under the plans was frozen on July 1, 2013 and December 31, 2009, respectively; 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 (including pension settlement expense) of the nonunion defined benefit pension plan, the SBP, and the postretirement health benefit plan are reported within the other line item of other income (costs). ​ The expense and liability related to the SBP and postretirement health benefit plan, and, prior to termination, the nonunion defined benefit pension plan, are measured based upon a number of assumptions and using the services of a third-party actuary. The discount rates used to discount the plans’ obligations are determined by matching projected cash distributions with appropriate high-quality corporate bond yields in a yield curve analysis. Prior to plan termination, the Company established the expected rate of return on plan assets for the nonunion defined benefit pension plan by considering the historical and expected returns for the plan’s current investment mix. Assumptions are also made regarding expected retirement age, mortality, employee turnover, and, for the postretirement health benefit plan, future increases in health care costs. The assumptions used directly impact the net periodic benefit cost 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 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. ​ The Company uses December 31 as the measurement date for the SBP, postretirement health benefit plan, and, prior to termination, the nonunion defined benefit pension plan. Plan obligations are also remeasured upon curtailment and upon settlement. ​ The Company recorded quarterly pension settlement expense related to the nonunion defined benefit pension plan when qualifying distributions determined to be settlements were expected to exceed the estimated total annual interest cost of the plan. Benefit distributions under the SBP individually exceed the annual interest cost of the plan, and 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. Pension settlement expense for the nonunion defined benefit pension plan and SBP is presented in Note J. ​ 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. Revenue adjustments may also occur due to rating or other billing adjustments. The Company estimates revenue adjustments based on historical information and revenue is recognized accordingly at the time of shipment. 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. ​ ArcBest Segment ArcBest segment revenues consist primarily of asset-light logistics services using third-party vendors to provide transportation services. ArcBest 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. ​ FleetNet Segment FleetNet segment revenues consist of service fee revenue, roadside repair revenue and routine maintenance services revenue. Service fee revenue for the FleetNet segment is recognized upon response to the service event. Repair and routine maintenance service revenue for the FleetNet segment is recognized upon completion of the service by third-party vendors. Revenue and expense from repair and maintenance services performed by third-party vendors are reported on a gross basis as FleetNet controls the services prior to transfer to the customer and remains primarily responsible to the customer for completion of the services. ​ 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: ​ Effective in 2020, the Company no longer had equity awards that were deemed participating securities. Basic earnings per share is calculated by dividing net income by the daily weighted number of shares of the Company’s common stock outstanding for the period. Diluted earnings per share is calculated using the treasury stock method. Under this method, the denominator used in calculating diluted earnings per share includes the impact of unvested restricted equity awards. ​ Share-Based Compensation: The fair value of restricted stock awards is determined based upon the closing market price of the Company’s common stock on the date of grant. The restricted stock units (“RSUs”) generally vest at the end of a five-year period following the date of grant for RSUs awarded prior to 2018, at the end of a four-year period following the date of grant for RSUs awarded in 2018 through 2020, and at the end of a three-year period following the date of grant for subsequent awards. Awards granted to non-employee directors typically vest at the end of a one-year period, subject to accelerated vesting due to death, disability, retirement, or change-in-control provisions. When RSUs become vested, the Company issues new shares which are subsequently distributed. Effective in 2020, the Company no longer had equity awards which were paid dividends or dividend equivalents during the vesting period. The Company recognizes the income tax benefits of dividends on share-based payment awards as income tax expense or benefit in the consolidated statements of operations when awards vest or are settled. ​ 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: ​ Adopted Accounting Pronouncements ​ ASC Topic 740, Income Taxes, ​ Accounting Pronouncements Not Yet Adopted ​ Management believes there is no new accounting guidance issued but not yet effective that would have a material impact to the Company’s current financial statements. ​

FINANCIAL INSTRUMENTS AND FAIR

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2021
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 ​ ​ 2021 ​ 2020 ​ ​ (in thousands) ​ Cash and cash equivalents ​ ​ ​ ​ ​ ​ ​ Cash deposits (1) ​ $ 72,790 ​ $ 240,687 ​ Variable rate demand notes (1)(2) ​ 230 ​ 29,066 ​ Money market funds (3) ​ 3,600 ​ 34,201 ​ Total cash and cash equivalents ​ $ 76,620 ​ $ 303,954 ​ ​ ​ ​ ​ ​ ​ ​ ​ Short-term investments ​ ​ ​ ​ ​ ​ ​ Certificates of deposit (1) ​ $ 48,339 ​ $ 53,297 ​ U.S. Treasury securities (4) ​ ​ — ​ ​ 12,111 ​ Total short-term investments ​ $ 48,339 ​ $ 65,408 ​ (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 primarily in FDIC-insured accounts and placing its short-term investments primarily in FDIC-insured certificates of deposit. However, certain cash deposits and certificates of deposit may exceed federally insured limits. At December 31, 2021 and 2020, cash, cash equivalents, and short-term investments totaling $42.6 million and $156.4 million, respectively, were neither FDIC insured nor direct obligations of the U.S. government. ​ ​ Fair value and carrying value disclosures of financial instruments as of December 31 are presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 ​ ​ (in thousands) ​ ​ ​ ​ Carrying ​ Fair ​ Carrying ​ Fair ​ ​ ​ ​ Value ​ Value ​ Value ​ Value ​ Credit Facility (1) ​ $ 50,000 ​ $ 50,000 ​ $ 70,000 ​ $ 70,000 ​ Notes payable (2) ​ 175,530 ​ 175,937 ​ 214,216 ​ 217,226 ​ New England Pension Fund withdrawal liability (3) ​ ​ 20,769 ​ ​ 23,521 ​ ​ 21,407 ​ ​ 25,523 ​ ​ ​ $ 246,299 ​ $ 249,458 ​ $ 305,623 ​ $ 312,749 ​ (1) The revolving credit facility (the “Credit Facility”) carries a variable interest rate based on LIBOR, plus a margin, that is considered to be 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 3.1% and 2.6% at December 31, 2021 and 2020, respectively, determined using the 20-year U.S. Treasury rate plus a spread (Level 2 of the fair value hierarchy). As of December 31, 2021, the outstanding withdrawal liability totaled $20.8 million, of which $0.7 million and $20.1 million was recorded in accrued expenses and other long-term liabilities, respectively. ​ ​ 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, 2021 ​ ​ ​ ​ ​ ​ 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) ​ $ 3,600 ​ $ 3,600 ​ $ — ​ $ — ​ Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan (2) ​ 3,848 ​ 3,848 ​ — ​ — ​ Interest rate swaps (3) ​ ​ 874 ​ ​ — ​ ​ 874 ​ ​ — ​ ​ ​ $ 8,322 ​ $ 7,448 ​ $ 874 ​ $ — ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps (3) ​ $ 455 ​ $ — ​ $ 455 ​ $ — ​ Contingent consideration (4) ​ ​ 93,700 ​ ​ — ​ ​ — ​ ​ 93,700 ​ ​ ​ $ 94,155 ​ $ — ​ $ 455 ​ $ 93,700 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ 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) ​ $ 34,201 ​ $ 34,201 ​ $ — ​ $ — ​ Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan (2) ​ 2,955 ​ 2,955 ​ — ​ — ​ ​ ​ $ 37,156 ​ $ 37,156 ​ $ — ​ $ — ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps (3) ​ $ 1,622 ​ $ — ​ $ 1,622 ​ $ — ​ ​ ​ (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 or other long-term liabilities. The fair values of the interest rate swaps were 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, 2021 and 2020 and considers the interest rate swap valuations in Level 2 of the fair value hierarchy. (4) Included in other long-term liabilities, based on when expected payouts become due. The estimated fair value of contingent consideration for an earn-out agreement related to the November 2021 acquisition of MoLo was determined by assessing Level 3 inputs. The Level 3 assessments utilize a Monte Carlo simulation with inputs including scenarios of estimated revenues and earnings before interest, taxes, depreciation and amortization to be achieved for the applicable performance periods, volatility factors applied to the simulations, and the discount rate applied, which was 9.0% as of December 2021. A 100 basis point decrease in the discount rate would increase the liability by $4.2 million. Subsequent changes to fair value as a result of recurring assessments will be recognized in operating income. ​ Assets Measured at Fair Value on a Nonrecurring Basis ​ There were no assets remeasured on a nonrecurring basis at December 31, 2021 or 2020.

ACQUISITION

ACQUISITION	12 Months Ended
	Dec. 31, 2021
ACQUISITION.
ACQUISITION	NOTE D – ACQUISITION ​ On November 1, 2021 (the “acquisition date”), the Company acquired MoLo Solutions, LLC (“MoLo”), a Chicago-based truckload freight brokerage company, pursuant to the Agreement and Plan of Merger (the “Merger Agreement”), dated September 29, 2021. Terms of the transaction included initial consideration paid at closing of $239.4 million, including and subject to certain post-closing adjustments which were estimated at closing and will be finalized post-closing. The Company funded the initial purchase price with cash on hand. The Merger Agreement provides for certain additional cash consideration to be paid by the Company based on the achievement of certain targets of adjusted earnings before interest, taxes, depreciation and amortization for each of the years ended December 31, 2023, 2024, and 2025. At 100% of the target, the cumulative additional consideration for years 2023 through 2025 would be $215.0 million, with the possible undiscounted cash consideration due ranging 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. ​ The following table represents the components of the total purchase consideration for the acquisition of MoLo. The Company recorded the estimated fair value of contingent consideration at the acquisition date as a part of the purchase price consideration for the acquisition (see Note B). The purchase consideration is preliminary and is dependent on final post-closing adjustments and completion of a net working capital audit. ​ ​ ​ ​ ​ ​ ​ ​ Purchase ​ ​ ​ Consideration ​ ​ ​ (in thousands) ​ Net cash consideration, including estimated post-closing adjustments ​ $ 239,398 ​ Contingent consideration ​ ​ 93,700 ​ Total purchase consideration ​ $ 333,098 ​ ​ 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 ArcBest operating segment (see Note N). 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. ​ The following table summarizes the estimated fair values of the acquired assets and liabilities at the acquisition date. The Company is in the process of making a final determination of acquired assets and liabilities, with remaining matters primarily related to finalization of a net working capital audit, thus, the provisional measurements are subject to change. ​ ​ ​ ​ ​ ​ ​ ​ Purchase ​ Allocation ​ ​ (in thousands) Accounts receivable, less allowances ​ $ 136,522 ​ Prepaid expenses ​ 766 ​ Property and equipment, net ​ 2,309 ​ Operating lease right-of-use assets ​ 844 ​ Intangible assets ​ 76,900 ​ Other assets ​ 323 ​ Total identifiable assets acquired ​ 217,664 ​ ​ ​ ​ ​ ​ Accounts payable ​ 94,909 ​ Accrued expenses and other current liabilities ​ 2,643 ​ Operating lease liabilities ​ 983 ​ Total liabilities ​ 98,535 ​ ​ ​ ​ ​ ​ Total identifiable net assets ​ 119,129 ​ Goodwill ​ 213,969 ​ Net assets acquired ​ $ 333,098 ​ ​ The MoLo acquisition has been accounted for as a business combination using the acquisition method of accounting (see Note B). The total purchase consideration to acquire MoLo has been allocated to the assets acquired and liabilities assumed as of November 1, 2021, with the excess purchase price recorded as goodwill. See Note E for further discussion of acquired goodwill and intangible assets. The estimated fair value of accounts receivable acquired was $136.5 million, having a gross contractual amount of $143.0 million as of November 1, 2021 and $6.5 million expected by the Company to be uncollectible. ​ 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 N). ​ The following unaudited pro forma supplemental information presents the Company’s consolidated results of operations as if the MoLo acquisition had occurred on January 1, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31 ​ ​ 2021 2020 ​ ​ (Unaudited) ​ ​ ​ (in thousands, except per share data) ​ ​ ​ ​ ​ ​ ​ ​ Revenues $ 4,488,564 ​ $ 3,213,722 ​ Income before income taxes ​ $ 266,866 ​ $ 63,622 ​ Net income ​ $ 205,728 ​ $ 48,290 ​ Diluted EPS ​ $ 7.68 ​ $ 1.83 ​ ​ The pro forma results of operations are based on historical information adjusted to include the pro forma effect of applying the Company’s accounting policies; adjusting interest expense and interest income for the initial cash consideration and elimination of MoLo debt; recording amortization expense related to the estimated fair value of intangibles acquired; eliminating the gain on debt forgiveness related to MoLo’s Payment Protection Program loan; eliminating transaction expenses related to the acquisition; and recording the related tax effects of these adjustments. The pro forma information is presented for illustrative purposes only and does not reflect either the realization of potential cost savings or any related integration costs. Certain business synergies and cost savings may result from the MoLo acquisition, although there can be no assurance these will be achieved. The pro forma information does not purport to be indicative of the results that would have actually been obtained if the acquisition had occurred as of the date indicated, nor does the pro forma information intend to be a projection of results that may be obtained in the future.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2021
GOODWILL AND INTANGIBLE ASSETS
GOODWILL AND INTANGIBLE ASSETS	NOTE E – GOODWILL AND INTANGIBLE ASSETS ​ Goodwill by reportable operating segment consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ArcBest FleetNet ​ ​ (in thousands) Balances at December 31, 2019 and 2020 ​ $ 88,320 ​ $ 87,690 ​ $ 630 ​ Goodwill acquired (1) ​ 213,969 ​ 213,969 ​ ​ — ​ Goodwill divested (2) ​ ​ (1,952) ​ ​ (1,952) ​ ​ — ​ Balances at December 31, 2021 ​ $ 300,337 ​ $ 299,707 ​ $ 630 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated impairment at December 31, 2021 ​ $ (20,000) ​ $ (20,000) ​ $ — ​ (1) Goodwill acquired relates to the acquisition of MoLo (see Note D). (2) Goodwill divested due to the sale of the labor services portion of the ArcBest segment’s moving business in second quarter 2021 was determined based on the relative fair value of the business sold to the total fair value of the reporting unit. ​ The Company performs the annual impairment evaluation of the goodwill balance of its reporting units, each October 1. As of October 1, 2021, the Company’s assessment of qualitative factors, including performance of the reporting units compared to prior periods, macroeconomic factors, industry considerations, and an increase in the Company’s market capitalization, led to a conclusion that goodwill was not impaired. As of October 1, 2020, the annual impairment evaluation determined there was no impairment of the goodwill balance. ​ As of the October 1, 2019 annual impairment testing, it was determined that the recorded balances of the domestic freight reporting unit within the ArcBest segment exceeded the estimated fair value of the reporting unit. As a result, the Company recorded a noncash goodwill impairment charge of $20.0 million in the ArcBest segment operating expenses for the year ended December 31, 2019. It was also determined that potential impairment indicators existed and an impairment test of the asset groups, including the Company’s finite-lived intangible assets was performed as of October 1, 2019. The Company recorded a noncash impairment charge of $6.5 million in the ArcBest segment operating expenses for the year ended December 31, 2019 to record the asset group at fair value. Approximately $6.0 million of the impairment was related to customer relationships and an additional $0.5 million was related to revenue equipment. The impairment resulted primarily from underperformance of the truckload and dedicated businesses within the domestic freight reporting unit of the ArcBest segment during 2019. Economic conditions during 2019, including lack of growth in the industrial and manufacturing sectors, tariff impacts of international trade, and higher customer inventory levels, contributed to uncertainty on projected shipment levels for purposes of these accounting assessments. ​ Intangible assets consisted of the following as of December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 ​ ​ 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 ​ $ 100,321 ​ $ 35,072 ​ $ 65,249 ​ $ 52,721 ​ $ 30,477 ​ $ 22,244 ​ Other ​ 8 ​ ​ 30,335 ​ ​ 1,304 ​ ​ 29,031 ​ ​ 980 ​ ​ 543 ​ ​ 437 ​ ​ 11 ​ 130,656 ​ 36,376 ​ 94,280 ​ ​ 53,701 ​ 31,020 ​ 22,681 ​ Indefinite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trade name N/A ​ 32,300 ​ N/A ​ 32,300 ​ ​ 32,300 ​ N/A ​ 32,300 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total intangible assets N/A ​ $ 162,956 ​ $ 36,376 ​ $ 126,580 ​ $ 86,001 ​ $ 31,020 ​ $ 54,981 ​ ​ ​ The annual impairment evaluation of indefinite-lived intangible assets was performed as of October 1, 2021 and 2020 and it was determined that there was no impairment of the recorded balances. ​ As of December 31, 2021, the future amortization for intangible assets acquired through business acquisitions were as follows: ​ ​ ​ ​ ​ ​ ​ Amortization of ​ ​ Intangible Assets ​ ​ (in thousands) ​ 2022 ​ $ 12,920 ​ 2023 ​ 12,826 ​ 2024 ​ 12,793 ​ 2025 ​ 12,778 ​ 2026 ​ ​ 8,671 ​ Thereafter ​ ​ 34,292 ​ Total amortization ​ $ 94,280 ​ ​

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2021
INCOME TAXES
INCOME TAXES	NOTE F – INCOME TAXES ​ Significant components of the provision or benefit for income taxes for the years ended December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands) Current provision: ​ ​ ​ ​ Federal ​ $ 56,451 ​ $ 10,001 ​ $ 2,202 ​ State ​ 14,430 ​ 3,267 ​ 1,813 ​ Foreign ​ 341 ​ 413 ​ 2,060 ​ ​ ​ 71,222 ​ 13,681 ​ 6,075 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred provision (benefit): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ (6,098) ​ 5,948 ​ 4,196 ​ State ​ (1,554) ​ 1,789 ​ 1,221 ​ Foreign ​ 63 ​ (22) ​ (6) ​ ​ ​ (7,589) ​ 7,715 ​ 5,411 ​ Total provision for income taxes ​ $ 63,633 ​ $ 21,396 ​ $ 11,486 ​ ​ 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 provision or benefit for the years ended December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 ​ 2019 ​ ​ (in thousands) Amortization, depreciation, and basis differences for property, plant and equipment and other long-lived assets (1) $ 1,451 $ 4,975 $ 16,255 ​ Amortization of intangibles and impairment ​ (536) ​ 183 ​ (6,933) ​ Changes in reserves for workers’ compensation, third-party casualty, and cargo claims ​ (3,294) ​ (182) ​ (1,880) ​ Revenue recognition ​ (1,445) ​ (1,481) ​ (1,437) ​ Allowance for credit losses ​ 156 ​ (652) ​ 541 ​ Nonunion pension and other retirement plans ​ (3) ​ 957 ​ 564 ​ Multiemployer pension fund withdrawal ​ ​ 164 ​ ​ 157 ​ ​ 150 ​ Federal and state net operating loss carryforwards utilized (generated) ​ (300) ​ (259) ​ 59 ​ State depreciation adjustments ​ 598 ​ 343 ​ (1,302) ​ Share-based compensation ​ (984) ​ (195) ​ (709) ​ Valuation allowance increase ​ 911 ​ 617 ​ 383 ​ Other accrued expenses ​ (4,097) ​ 1,663 ​ (699) ​ Prepaid expenses ​ ​ (788) ​ ​ 1,207 ​ ​ 1,782 ​ Operating lease right-of-use assets/liabilities – net ​ ​ (228) ​ ​ (13) ​ ​ (1,049) ​ Other ​ 806 ​ 395 ​ (314) ​ Deferred tax provision (benefit) ​ $ (7,589) ​ $ 7,715 ​ $ 5,411 ​ (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 a decrease in the purchase of assets eligible for 100% depreciation, the deferred tax expense related to the tax depreciation expense in excess of book depreciation decreased over the three-year period from 2019 through 2021. ​ Significant components of the deferred tax assets and liabilities at December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 ​ ​ (in thousands) Deferred tax assets: ​ ​ ​ Accrued expenses ​ $ 47,683 ​ $ 40,502 ​ Operating lease liabilities ​ ​ 30,590 ​ ​ 33,933 ​ Supplemental pension liabilities ​ ​ 97 ​ ​ 103 ​ Multiemployer pension fund withdrawal ​ ​ 5,247 ​ ​ 5,409 ​ Postretirement liabilities other than pensions ​ 4,441 ​ 4,871 ​ Share-based compensation ​ 6,755 ​ 5,827 ​ Federal and state net operating loss carryovers ​ 1,652 ​ 1,353 ​ Revenue recognition ​ ​ 2,778 ​ ​ 1,426 ​ Other ​ 266 ​ 1,297 ​ Total deferred tax assets ​ 99,509 ​ 94,721 ​ Valuation allowance ​ (2,196) ​ (1,284) ​ Total deferred tax assets, net of valuation allowance ​ 97,313 ​ 93,437 ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ ​ Amortization, depreciation, and basis differences for property, plant and equipment, and other long-lived assets ​ 114,999 ​ 113,092 ​ Operating lease right-of-use assets ​ ​ 29,403 ​ ​ 32,923 ​ Intangibles ​ 6,966 ​ 7,520 ​ Prepaid expenses ​ 5,368 ​ 6,151 ​ Total deferred tax liabilities ​ 156,736 ​ 159,686 ​ Net deferred tax liabilities ​ $ (59,423) ​ $ (66,249) ​ ​ Reconciliation between the effective income tax rate, as computed on income before income taxes, and the statutory federal income tax rate for the years ended December 31 is presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 ​ 2019 ​ ​ (in thousands, except percentages) Income tax provision at the statutory federal rate of 21.0% $ 58,202 $ 19,424 $ 10,809 ​ Federal income tax effects of: ​ ​ ​ ​ ​ ​ ​ ​ ​ State income taxes ​ (2,704) ​ (1,062) ​ (637) ​ Nondeductible expenses ​ 3,596 ​ 1,395 ​ 1,344 ​ Life insurance proceeds and changes in cash surrender value ​ (866) ​ (488) ​ (775) ​ Alternative fuel credit ​ — ​ (1,261) ​ (2,340) ​ Net increase in valuation allowances ​ 887 ​ 617 ​ 382 ​ Net increase (decrease) in uncertain tax positions ​ ​ 854 ​ ​ (933) ​ ​ (20) ​ Settlement of share-based compensation ​ ​ (6,140) ​ ​ 420 ​ ​ 388 ​ Nonunion pension termination expense ​ ​ — ​ ​ — ​ ​ 1,040 ​ Foreign tax credits generated ​ ​ (404) ​ ​ (391) ​ ​ (2,054) ​ Federal research and development tax credits ​ ​ (2,044) ​ ​ (2,078) ​ ​ (1,354) ​ Other ​ (1,028) ​ 306 ​ (385) ​ Federal income tax provision ​ 50,353 ​ 15,949 ​ 6,398 ​ State income tax provision ​ 12,876 ​ 5,056 ​ 3,034 ​ Foreign income tax provision ​ 404 ​ 391 ​ 2,054 ​ Total provision for income taxes ​ $ 63,633 ​ $ 21,396 ​ $ 11,486 ​ Effective tax rate ​ 23.0 % 23.1 % 22.3 % ​ Income taxes paid, excluding income tax refunds, totaled $77.5 million, $28.6 million, and $28.1 million in 2021, 2020, and 2019, respectively. Income tax refunds totaled $19.4 million, $13.3 million, and $13.1 million in 2021, 2020, and 2019, respectively. ​ Under ASC Topic 718, Compensation – Stock Compensation ​ At December 31, 2021, the Company had gross federal net operating loss carryforwards of $1.0 million. Due to taxable income, there is no need for a valuation allowance on these amounts at December 31, 2021, and the related valuation allowance of $0.1 million was removed. At December 31, 2021, the Company had total gross state net operating losses of $19.3 million. Gross state net operating losses of $3.4 million are from the acquisition of Panther Expedited Services, Inc. (“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 to 20 years . Gross state net operating losses of $14.8 million are for subsidiaries that have had taxable losses for three or more prior tax years or have other nexus issues that reduce the likelihood of the utilization of the losses. These net operating loss carryforwards have been fully reserved with valuation allowances of $1.1 million and $0.6 million at December 31, 2021 and 2020, respectively. Additional valuation allowances of $0.2 million related to state research and development tax credits were reserved at December 31, 2021 and 2020, and less than $0.1 million related to state interest expense carryforwards was reserved at December 31, 2021. ​ 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 $0.8 million and $0.4 million at December 31, 2021 and 2020, respectively. ​ Consolidated federal income tax returns filed for tax years through 2017 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, 2021. ​ At December 31, 2021, a reserve for uncertain tax positions of $0.9 million was established related to credits taken on federal returns. There was no reserve for uncertain tax positions at December 31, 2020. ​ For 2021, 2020, and 2019, interest paid or accrued related to foreign and state income taxes was immaterial.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2021
LEASES
LEASES	​ NOTE G – LEASES ​ The Company leases, under finance and operating lease arrangements, certain facilities used primarily in the Asset-Based segment service center operations, certain revenue equipment used in the ArcBest segment operations, and certain other office equipment. Current operating leases have remaining terms of less than 11.1 years, some of which include one or more options to renew, with renewal option terms up to five years . There are no available termination options as of December 31, 2021. The right-of-use assets and lease liabilities as of December 31, 2021 and 2020 do not assume the option to early terminate any of the Company’s leases, and all renewal options that have been exercised or are reasonably certain to be exercised as of December 31, 2021 and 2020 are included in the right-of-use assets and lease liabilities. Variable lease cost for operating leases consists of subsequent changes in the CPI 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 ​ 2021 2020 2019 ​ ​ (in thousands) Operating lease expense ​ $ 26,552 ​ $ 24,559 ​ $ 22,291 Variable lease expense ​ ​ 4,128 ​ ​ 3,152 ​ ​ 3,366 Sublease income ​ ​ (626) ​ ​ (398) ​ ​ (324) Total operating lease expense (1) ​ $ 30,054 ​ $ 27,313 ​ $ 25,333 (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 ​ ​ ​ 2021 ​ 2020 2019 ​ ​ ​ (in thousands) ​ Noncash change in operating right-of-use assets ​ $ 24,023 ​ $ 21,184 ​ $ 20,439 ​ Change in operating lease liabilities ​ ​ (23,400) ​ ​ (20,428) ​ ​ (19,711) ​ Operating right-of-use-assets and lease liabilities, net ​ $ 623 ​ $ 756 ​ $ 728 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid for amounts included in the measurement of operating lease liabilities ​ $ (25,909) ​ $ (23,810) ​ $ (21,714) ​ ​ Supplemental balance sheet information related to operating leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ ​ (in thousands, except lease term and discount rate) ​ ​ ​ ​ ​ Land and ​ Equipment ​ ​ ​ Total ​ Structures ​ and Others Operating right-of-use assets (long-term) ​ $ 106,686 ​ $ 106,394 ​ $ 292 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease liabilities (current) ​ $ 22,740 ​ $ 22,477 ​ $ 263 Operating lease liabilities (long-term) ​ 88,835 ​ ​ 88,810 ​ ​ 25 Total operating lease liabilities ​ $ 111,575 ​ $ 111,287 ​ $ 288 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term (in years) ​ ​ 6.9 ​ ​ ​ ​ ​ ​ Weighted-average discount rate ​ ​ 2.88% ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ (in thousands, except lease term and discount rate) ​ ​ ​ ​ ​ ​ Land and ​ Equipment ​ ​ ​ ​ Total ​ Structures ​ and Others ​ Operating right-of-use assets (long-term) ​ $ 115,195 ​ $ 114,908 ​ $ 287 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease liabilities (current) ​ $ 21,482 ​ $ 21,207 ​ $ 275 ​ Operating lease liabilities (long-term) ​ 97,839 ​ ​ 97,828 ​ ​ 11 ​ Total operating lease liabilities ​ $ 119,321 ​ $ 119,035 ​ $ 286 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term (in years) ​ ​ 6.7 ​ ​ ​ ​ ​ ​ ​ Weighted-average discount rate ​ ​ 3.18% ​ ​ ​ ​ ​ ​ ​ ​ Maturities of operating lease liabilities at December 31, 2021 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equipment ​ ​ ​ ​ ​ ​ Land and ​ and ​ ​ Total Structures (1) Other ​ (in thousands) ​ 2022 ​ $ 25,567 ​ $ 25,302 ​ $ 265 ​ 2023 ​ 19,800 ​ 19,775 ​ 25 ​ 2024 ​ 17,414 ​ 17,414 ​ — ​ 2025 ​ 14,839 ​ 14,839 ​ — ​ 2026 ​ 11,404 ​ 11,404 ​ — ​ Thereafter ​ 33,750 ​ 33,750 ​ — ​ Total lease payments ​ ​ 122,774 ​ ​ 122,484 ​ ​ 290 ​ Less imputed interest ​ ​ (11,199) ​ ​ (11,197) ​ ​ (2) ​ Total ​ $ 111,575 ​ $ 111,287 ​ $ 288 ​ ​ (1) Excludes future minimum lease payments for leases which were executed but had not yet commenced as of December 31, 2021 of $85.3 million which will be paid over 10 - 12 years . The Company plans to take possession of the leased spaces during 2022 .

LONG-TERM DEBT AND FINANCING AR

LONG-TERM DEBT AND FINANCING ARRANGEMENTS	12 Months Ended
	Dec. 31, 2021
LONG-TERM DEBT AND FINANCING ARRANGEMENTS
LONG-TERM DEBT AND FINANCING ARRANGEMENTS	​ NOTE H – 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 and finance lease obligations related to the financing of revenue equipment (tractors and trailers used primarily in Asset-Based segment operations), certain other equipment, and software as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 ​ December 31 ​ ​ 2021 2020 ​ ​ (in thousands) ​ Credit Facility (interest rate of 1.2% (1) ​ $ 50,000 ​ $ 70,000 ​ Notes payable (weighted-average interest rate of 2.4% at December 31, 2021) ​ 175,530 ​ 214,216 ​ Finance lease obligations (weighted-average interest rate of 3.3% at December 31, 2021) ​ 2 ​ 8 ​ ​ ​ 225,532 ​ 284,224 ​ Less current portion ​ 50,615 ​ 67,105 ​ Long-term debt, less current portion ​ $ 174,917 ​ $ 217,119 ​ (1) The interest rate swap mitigates interest rate risk by effectively converting $50.0 million of borrowings under the Credit Facility from variable-rate interest to fixed-rate interest with a per annum rate of 3.12% based on the margin of the Credit Facility as of December 31, 2021 and 2020. ​ Scheduled maturities of long term debt obligations as of December 31, 2021 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Credit Notes Finance Lease ​ ​ ​ Total ​ Facility (1) ​ Payable ​ Obligations ​ ​ ​ (in thousands) ​ 2022 ​ $ 55,060 ​ $ 807 ​ $ 54,251 ​ $ 2 ​ 2023 ​ 51,599 ​ 1,213 ​ ​ 50,386 ​ — ​ 2024 ​ 95,675 ​ 51,028 ​ ​ 44,647 ​ — ​ 2025 ​ 22,856 ​ — ​ ​ 22,856 ​ — ​ 2026 ​ 10,898 ​ ​ — ​ ​ 10,898 ​ ​ — ​ Thereafter ​ 293 ​ ​ — ​ ​ 293 ​ ​ — ​ Total payments ​ 236,381 ​ 53,048 ​ ​ 183,331 ​ 2 ​ Less amounts representing interest ​ 10,849 ​ 3,048 ​ 7,801 ​ — ​ Long-term debt ​ $ 225,532 ​ $ 50,000 ​ $ 175,530 ​ $ 2 ​ (1) The future interest payments included in the scheduled maturities due are calculated using variable interest rates based on the LIBOR swap curve, plus the anticipated applicable margin. ​ ​ Assets securing notes payable or held under finance leases at December 31 were included in property, plant and equipment as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 ​ December 31 ​ ​ 2021 2020 ​ ​ (in thousands) Revenue equipment $ 241,892 $ 326,823 ​ Service, office, and other equipment ​ ​ 29,773 ​ ​ 26,270 ​ Total assets securing notes payable or held under finance leases ​ 271,665 ​ 353,093 ​ Less accumulated depreciation and amortization (1) ​ 88,696 ​ 115,424 ​ Net assets securing notes payable or held under finance leases ​ $ 182,969 ​ $ 237,669 ​ (1) Amortization of assets held under finance leases and depreciation of assets securing notes payable are included in depreciation expense . ​ The Company’s long-term debt obligations have a weighted-average interest rate of 2.6% at December 31, 2021. The Company paid interest of $8.7 million, $11.3 million, and $10.9 million in 2021, 2020, and 2019, respectively, net of capitalized interest which totaled $0.5 million, $0.3 million, and $0.2 million for 2021, 2020, and 2019, respectively. ​ Financing Arrangements ​ Credit Facility The Company has a revolving credit facility (the “Credit Facility”) under its Third Amended and Restated Credit Agreement (the “Credit Agreement”) with an initial maximum credit amount of $250.0 million, including a swing line facility in an aggregate amount of up to $25.0 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 certain additional conditions as provided in the Credit Agreement. The Company borrowed $50.0 million and repaid $70.0 million of borrowings under the Credit Facility during 2021. As of December 31, 2021, the Company had available borrowing capacity of $200.0 million under the initial maximum credit amount of the Credit Facility. In February 2022, the Company borrowed $65.0 million under the Credit Facility, including $10.0 million of borrowings under the swing line facility. ​ Principal payments under the Credit Facility are due upon maturity of the facility on October 1, 2024; 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; or (ii) at a Eurodollar Rate (as defined in the Credit Agreement) plus a spread. 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, purchases and sales of assets, and certain restricted payments. The Company was in compliance with the covenants under the Credit Agreement at December 31, 2021. ​ Interest Rate Swaps The Company has an interest rate swap agreement with a $50.0 million notional amount which started on January 2, 2020 and will mature on June 30, 2022. The Company receives floating rate interest amounts based on one -month LIBOR in exchange for fixed-rate interest payments of 1.99% over the life of the agreement. The interest rate swap mitigates interest rate risk by effectively converting $50.0 million of borrowings under the Credit Facility from variable rate interest to fixed rate interest with a per annum rate of 3.12% based on the margin of the Credit Facility as of December 31, 2021. The fair value of the interest rate swap of $0.5 million and $1.4 million was recorded in other long-term liabilities at December 31, 2021 and 2020, respectively. ​ The Company also has an interest rate swap agreement with a $50.0 million notional amount which will start on June 30, 2022 and mature on October 1, 2024. The Company will receive floating-rate interest amounts based on one-month LIBOR in exchange for fixed-rate interest payments of 0.43% beginning on June 30, 2022 throughout the remaining term of the agreement. From June 30, 2022 to October 1, 2024, the extended interest rate swap agreement will effectively convert $50.0 million of borrowings under the Credit Facility from variable-rate interest to fixed-rate interest with a per annum rate of 1.56% based on the margin of the Credit Facility as of December 31, 2021. The fair value of the interest rate swap of $0.9 million was recorded in other long-term assets and $0.2 million was recorded in other long-term liabilities at December 31, 2021 and 2020, respectively. ​ The unrealized gain or loss on the interest rate swap instruments was reported as a component of accumulated other comprehensive income, net of tax, in stockholders’ equity at December 31, 2021 and 2020, and the change in the unrealized gain or loss on the interest rate swaps for the years ended December 31, 2021 and 2020 was reported in other comprehensive income, net of tax, in the consolidated statements of comprehensive income. The interest rate swaps are 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 agreements at December 31, 2021. ​ Accounts Receivable Securitization Program In the second quarter of 2021, the Company amended and restated its accounts receivable securitization program. The amendment extended the maturity date of the program from October 1, 2021 to July 1, 2024, decreased the amount of available cash proceeds under the facility from $125.0 million to $50.0 million and increased the amount of additional borrowings the Company may request under the accordion feature from $25.0 million to $100.0 million, subject to certain conditions. ​ 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 accounts receivable securitization program bear interest based upon LIBOR, 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, 2021. ​ 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, 2021, standby letters of credit of $10.0 million have been issued under the program, which reduced the available borrowing capacity to $40.0 million. ​ Letter of Credit Agreements and Surety Bond Programs As of December 31, 2021 and 2020, the Company had letters of credit outstanding of $10.6 million and $12.3 million, respectively, (including $10.0 million and $11.7 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, 2021 and 2020, surety bonds outstanding related to the self-insurance program totaled $50.9 million and $61.7 million, respectively. ​ Notes Payable The Company has financed the purchase of certain revenue equipment, other equipment, and software through promissory note arrangements, including $59.7 million and $61.8 million for revenue equipment and other equipment during the year ended December 31, 2021 and 2020, respectively. ​ Subsequent to December 31, 2021, the Company financed the purchase of an additional $6.2 million of revenue equipment through promissory note arrangements as of late-February 2022.

ACCRUED EXPENSES

ACCRUED EXPENSES	12 Months Ended
	Dec. 31, 2021
ACCRUED EXPENSES.
ACCRUED EXPENSES	NOTE I – ACCRUED EXPENSES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 ​ ​ 2021 2020 ​ ​ ​ (in thousands) ​ Workers’ compensation, third-party casualty, and loss and damage claims reserves ​ $ 116,535 ​ $ 103,898 ​ Accrued vacation pay ​ 52,746 ​ 51,728 ​ Accrued compensation, including retirement benefits ​ ​ 110,755 ​ ​ 67,690 ​ Taxes other than income ​ 10,225 ​ 10,468 ​ Other ​ 15,590 ​ 12,962 ​ Total accrued expenses ​ $ 305,851 ​ $ 246,746 ​ ​

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	12 Months Ended
	Dec. 31, 2021
EMPLOYEE BENEFIT PLANS
EMPLOYEE BENEFIT PLANS	NOTE J – EMPLOYEE BENEFIT PLANS ​ Nonunion Defined Benefit Pension, Supplemental Benefit, and Postretirement Health Benefit Plans ​ The Company had a noncontributory defined benefit pension plan covering substantially all noncontractual employees hired before January 1, 2006. In June 2013, the Company amended the nonunion defined benefit pension plan to freeze the participants’ final average compensation and years of credited service as of July 1, 2013. ​ In November 2017, an amendment was executed to terminate the nonunion defined benefit pension plan with a termination date of December 31, 2017. In September 2018, the plan received a favorable determination letter from the IRS regarding qualification of the plan termination. The plan distributed immediate lump sum benefit payments related to the plan termination in 2018 and 2019. The plan purchased a nonparticipating annuity contract from an insurance company during 2019 to settle the pension obligation related to the vested benefits of plan participants and beneficiaries who were either receiving monthly benefit payments at the time of the contract purchase or who did not elect to receive a lump sum benefit upon plan termination. The remaining benefit obligation for the vested benefits of plan participants who could not be located for payment was transferred to the Pension Benefit Guaranty Corporation (the “PBGC”). Termination of the nonunion defined benefit plan was completed in 2019 and the plan was liquidated as of December 31, 2019. ​ The Company recognized ​ The Company has an unfunded supplemental benefit plan (the “SBP”) which was designed to supplement benefits under the Company’s nonunion defined benefit pension plan for designated executive officers. The SBP was closed to new entrants, and a cap was closed on the maximum payment per participant to existing participants 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. As presented in the tables within this Note, pension settlement expense and a corresponding reduction in the net actuarial loss was recorded in 2020 and 2019 related to lump-sum SBP benefit distributions. The SBP did not incur pension settlement expense in 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. Effective January 1, 2011, retirees began paying a portion of the premiums under the plan according to age and coverage levels. The amendment to the plan to implement retiree premiums resulted in an unrecognized prior service credit which was recorded in accumulated other comprehensive loss and was amortized over approximately nine years . The prior service credit was fully amortized as of December 31, 2020. ​ 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 ​ 2021 2020 2021 2020 ​ ​ (in thousands) Change in benefit obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Benefit obligations, beginning of year ​ $ 392 ​ $ 3,236 ​ $ 18,751 ​ $ 20,630 ​ Service cost ​ — ​ — ​ 192 ​ 187 ​ Interest cost ​ 4 ​ 9 ​ 427 ​ 576 ​ Actuarial (gain) loss (1) ​ (15) ​ 34 ​ (1,736) ​ (2,027) ​ Benefits paid ​ — ​ (2,887) ​ (642) ​ (615) ​ Benefit obligations, end of year ​ 381 ​ 392 ​ 16,992 ​ 18,751 ​ Change in plan assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value of plan asset, beginning of year ​ — ​ — ​ — ​ — ​ Employer contributions ​ — ​ 2,887 ​ 642 ​ 615 ​ Benefits paid ​ — ​ (2,887) ​ (642) ​ (615) ​ Fair value of plan assets, end of year ​ — ​ — ​ — ​ — ​ Funded status at period end ​ $ (381) ​ $ (392) ​ $ (16,992) ​ $ (18,751) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated benefit obligation ​ $ 381 ​ $ 392 ​ $ 16,992 ​ $ 18,751 ​ (1) The actuarial gain on the postretirement health benefit plan for 2021 and 2020 is primarily related to the impact of actuarial assumptions on the valuation of plan costs. For 2021, these actuarial assumptions include an increase in the discount rate used to remeasure the plan obligation at December 31, 2021 versus December 31, 2020 and lower actual healthcare premium costs versus the assumed trend rates. For 2020, these actuarial assumptions include lower health care cost trend rates, partially offset by a decrease in the discount rate used to remeasure the plan obligation at December 31, 2020 versus December 31, 2019. ​ Amounts recognized in the consolidated balance sheets at December 31 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2021 2020 2021 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current portion of pension and postretirement liabilities ​ $ — ​ $ — ​ $ (640) ​ $ (588) ​ Pension and postretirement liabilities, less current portion ​ (381) ​ (392) ​ (16,352) ​ (18,163) ​ Liabilities recognized ​ $ (381) ​ $ (392) ​ $ (16,992) ​ $ (18,751) ​ ​ 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: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nonunion Defined ​ Supplemental ​ Postretirement ​ ​ ​ Benefit Pension Plan ​ Benefit Plan ​ Health Benefit Plan ​ ​ 2021 2020 2019 2021 2020 2019 2021 2020 2019 ​ ​ (in thousands) ​ ​ ​ Service cost ​ $ — ​ $ — ​ $ — ​ $ — ​ $ — ​ $ — ​ $ 192 ​ $ 187 ​ $ 320 ​ Interest cost ​ — ​ — ​ 624 ​ 4 ​ 9 ​ 39 ​ 427 ​ 576 ​ 1,212 ​ Expected return on plan assets ​ ​ — ​ ​ — ​ ​ (31) ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ Amortization of prior service credit ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (1) ​ ​ (33) ​ Pension settlement expense (1) ​ ​ — ​ ​ — ​ ​ 4,164 ​ ​ — ​ ​ 89 ​ ​ 370 ​ ​ — ​ ​ — ​ ​ — ​ Amortization of net actuarial (gain) loss (2) ​ — ​ — ​ 260 ​ 9 ​ 8 ​ 95 ​ (548) ​ (597) ​ 898 ​ Net periodic benefit cost ​ $ — ​ $ — ​ $ 5,017 ​ $ 13 ​ $ 106 ​ $ 504 ​ $ 71 ​ $ 165 ​ $ 2,397 ​ (1) For 2019, the presentation of pension settlement expense excludes a $4.0 million noncash pension termination expense which is further described within this Note. (2) 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. ​ The following is a summary of the pension settlement distributions and pension settlement expense for the years ended December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nonunion Defined ​ Supplemental ​ ​ Benefit Pension Plan ​ Benefit Plan ​ 2021 2020 2019 (1) 2021 2020 (2) 2019 (3) ​ ​ (in thousands, except per share data) Pension settlement distributions ​ $ — ​ $ — ​ $ 33,938 ​ $ — ​ $ 2,887 ​ $ 937 ​ Pension settlement expense, pre-tax (4) ​ $ — ​ $ — ​ $ 4,164 ​ $ — ​ $ 89 ​ $ 370 ​ Pension settlement expense per diluted share, net of taxes ​ $ — ​ $ — ​ $ 0.12 ​ $ — ​ $ — ​ $ 0.01 ​ (1) Pension settlement distributions for 2019 represent $18.4 million of lump-sum benefit distributions, including participant-elected distributions associated with the plan’s termination, a $14.0 million nonparticipating annuity contract purchase, and a $1.5 million transfer of benefit obligations to the PBGC. (2) The 2020 SBP distributions include the portion of a benefit related to an officer retirement that occurred in 2019 which was delayed for six months after retirement in accordance with IRC Section 409A. (3) The 2019 SBP distribution excludes the portion of the benefit related to an officer retirement which was delayed for six months after retirement in accordance with IRC Section 409A. The pension settlement expense related to the delayed distribution was recognized in 2019. (4) For 2019, the presentation of pension settlement expense excludes a $4.0 million noncash pension termination expense which is further described within this Note. ​ 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 ​ 2021 2020 2021 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net actuarial (gain) loss ​ $ 40 ​ $ 64 ​ $ (5,642) ​ $ (4,454) ​ ​ 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 ​ 2021 2020 2021 2020 Discount rate ​ 1.8 % 1.1 % 2.7 % 2.3 % ​ 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: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nonunion Defined ​ Supplemental ​ Postretirement ​ ​ Benefit Pension Plan ​ Benefit Plan ​ Health Benefit Plan ​ 2021 2020 2019 (1) 2021 2020 2019 2021 2020 2019 Discount rate ​ N/A ​ N/A ​ 3.9 % 1.1 % 2.4 % 3.6 % 2.3 % 3.1 % 4.2 % Expected return on plan assets ​ N/A ​ N/A ​ 1.4 % N/A N/A N/A N/A N/A N/A ​ (1) The discount rate presented was used to determine the first quarter 2019 expense, and the short-term discount rate established upon quarterly settlements in 2019 of 3.8% and 3.7% , was used to calculate the expense for the second and third quarter of 2019, respectively. The expected return on plan assets presented was used to determine nonunion pension expense for first quarter 2019, and no expected return on plan assets was assumed for the second and third quarters of 2019. ​ The assumed health care cost trend rates for the Company’s postretirement health benefit plan at December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 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 2033 2032 (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, 2021 and 2020 are for 2023 and 2022, 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, 2021 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental Postretirement ​ ​ Benefit ​ Health ​ ​ Plan ​ Benefit Plan ​ ​ ​ ​ ​ ​ ​ 2022 ​ $ — ​ $ 640 ​ 2023 ​ $ — ​ $ 633 ​ 2024 ​ $ — ​ $ 584 ​ 2025 ​ $ — ​ $ 605 ​ 2026 ​ $ — ​ $ 642 ​ 2027-2031 ​ $ 424 ​ $ 3,522 ​ ​ Deferred Compensation Plans ​ The Company has deferred salary agreements with certain executives for which liabilities of $1.5 million and $1.8 million were recorded as of December 31, 2021 and 2020, 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, 2021 and 2020, VSP balances of $3.8 million and $3.0 million, respectively, were included in other long-term assets with a corresponding amount recorded in other long-term 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 $7.7 million, $4.6 million, and $6.8 million for 2021, 2020, and 2019, respectively. The Company’s matching expense for 2020 was impacted by the cost reduction actions implemented in April 2020 in response to the COVID-19 pandemic, which included suspension of the employer match on the nonunion 401(k) plans for the second quarter of 2020. The plans also allow for discretionary 401(k) Company contributions determined annually. The Company recognized expense of $16.8 million, $12.6 million, and $10.9 million in 2021, 2020, and 2019, respectively, related to its discretionary contributions to the nonunion defined contribution 401(k) plans. The increase in expense for 2021 is primarily related to a higher discretionary contribution rate, compared to 2020. 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, 2021, 2020, and 2019, $28.3 million, $14.2 million, $13.7 million, respectively, were accrued for future payments under the plans. ​ Other Plans ​ Other long-term assets include $57.2 million and $55.7 million at December 31, 2021 and 2020, 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 $4.1 million, $2.3 million, and $3.7 million for 2021, 2020, and 2019, respectively, 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 Taft-Hartley Act, to provide benefits for its contractual employees. ABF Freight’s contributions generally are based on the time worked by its contractual employees, in accordance with the 2018 ABF NMFA and other related supplemental agreements. ABF Freight recognizes as expense the contractually required contributions for each period and recognizes as a liability any contributions due and unpaid. ​ 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. Contribution obligations to these plans are generally specified in the 2018 ABF NMFA, which will remain in effect through June 30, 2023. The funding obligations to the pension plans are intended to satisfy the requirements imposed by the Pension Protection Act of 2006 (the “PPA”), which was permanently extended by the Multiemployer Pension Reform Act (the “Reform Act”) included in the Consolidated and Further Continuing Appropriations Act of 2015. Through the term of its current collective bargaining agreement, ABF Freight’s contribution obligations generally will be satisfied by making the specified contributions when due. However, the Company cannot determine with any certainty the contributions that will be required under future collective bargaining agreements for ABF Freight’s contractual employees. ​ 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 - correct funding issues, subject to various requirements and restrictions, including applying to the U.S. Department of Treasury (the “Treasury Department”) for the reduction of certain accrued benefits. ​ 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 ​ Based on the most recent annual funding notices the Company has received, most of which are for plan year ended December 31, 2020 and prior to financial assistance from the Pension Relief Act, approximately 56% of ABF Freight’s multiemployer pension plan contributions for the year ended December 31, 2021 were made to plans that are in “critical and declining status,” including the Central States Pension Plan discussed below, approximately 4% were made to plans that are in “critical status” but not “critical and declining status,” and approximately 4% 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 severity of a plan’s underfunded status, which was prior to financial assistance from the Pension Relief Act, was also considered in the analysis of individually significant funds to be separately disclosed. ​ 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) 2021 2020 Implemented (c) 2021 2020 2019 Imposed (e) Central States, Southeast and Southwest Areas Pension Plan (1)(2) 36-6044243 Critical and Declining Critical and Declining Implemented (3) ​ $ 71,045 ​ $ 68,704 ​ $ 75,803 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Western Conference of Teamsters Pension Plan (2) 91-6145047 Green Green No ​ 25,861 ​ 23,633 ​ 24,860 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Central Pennsylvania Teamsters Defined Benefit Plan (1)(2) 23-6262789 Green Green No ​ 13,931 ​ 13,485 ​ 13,907 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ I. B. of T. Union Local No. 710 Pension Fund (5)(6) 36-2377656 Green (4) Green (4) No ​ 9,553 ​ 9,885 ​ 10,164 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ New England Teamsters Pension Fund (7)(8) 04-6372430 Critical and Declining (9) Critical and Declining (9) Implemented (10) ​ 4,357 ​ 4,464 ​ 4,802 ​ No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ All other plans in the aggregate ​ ​ ​ ​ ​ ​ ​ ​ ​ 22,146 ​ 22,023 ​ 24,210 ​ ​ Total multiemployer pension contributions paid (11) ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 146,893 ​ $ 142,194 ​ $ 153,746 ​ ​ 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 2021 and 2020 is for the plan’s year-end status at December 31, 2020 and 2019, 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. ​ (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, 2020 and 2019. (2) 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, 2020 and 2019. (3) Adopted a rehabilitation plan effective March 25, 2008 as updated. Utilized amortization extension granted by the IRS effective December 31, 2003. (4) PPA zone status relates to plan years February 1, 2020 – January 31, 2021 and February 1, 2019 – January 31, 2020. (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, 2020. (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, 2021 and 2020. (7) Contributions include $1.6 million for 2021, 2020, and 2019, respectively, 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 period of 23 years . (8) 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, 2020 and 2019. (9) PPA zone status relates to plan years October 1, 2020 – September 30, 2021 and October 1, 2019 – September 30, 2020. (10) Adopted a rehabilitation plan effective January 1, 2009. (11) 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 2018 ABF NMFA 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 business levels. Due to the negative impact of the COVID-19 pandemic on tonnage levels, most significantly in the second quarter of 2020, the Company made operational changes in the Asset-Based network in the second and third quarters of 2020, including workforce reductions to better align resources with business levels. The reduction in hours worked by a portion of ABF Freight’s contractual employees contributed to lower contributions to multiemployer pension plans for 2020. An increase in hours worked by ABF Freight’s contractual employees in 2021, as well as additional contractual employees hired primarily in the second half of the year, to service higher shipment levels in response to increased customer demand resulted in an increase in multiemployer pension contributions for 2021, compared to 2020. ​ For 2021, 2020, and 2019, 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 19.5% , and 24.8% as of January 1, 2020 and 2019, respectively. ABF Freight received a Notice of Critical and Declining Status for the Central States Pension Plan dated March 30, 2021, in which the plan’s actuary certified that, as of January 1, 2021, the plan is in critical and declining status, as defined by the Reform Act. Although the future of the Central States Pension Plan is impacted by a number of factors, without legislative action, the plan is currently projected to become insolvent within 4 years . ​ Prior to 2020, the Company received notices that a reduction of benefits was authorized by the Treasury Department for the Western Pennsylvania Teamsters and Employers Pension Fund and the New York State Teamsters Conference Pension and Retirement Fund. 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. Approximately 1% of ABF Freight’s total multiemployer pension contributions for the year ended December 31, 2021 were made to each of these funds. During 2020, the Company received a notice of insolvency for the Trucking Employees of North Jersey Welfare Fund, Inc. – Pension Fund (the “North Jersey Welfare Fund”), to which the PBGC will provide financial assistance by paying retiree benefits not to exceed the PBGC guarantee limits for insolvent multiemployer plans. Approximately 2% of ABF Freight’s total multiemployer pension contributions for the year ended December 31, 2021, were made to the North Jersey Welfare Fund. ​ 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 $176.2 million, $163.8 million, and $172.0 million, for the year ended December 31, 2021, 2020, and 2019, respectively. The benefit contribution rate for health and welfare benefits increased by an average of approximately 4.3%, 4.0%, and 3.9% primarily on August 1, 2021, 2020, and 2019, respectively, under the ABF Freight’s collective bargaining agreement with the IBT. ​ Due to the negative impact of the COVID-19 pandemic on tonnage levels, the Company made operational changes in the Asset-Based network in the second and third quarters of 2020, including workforce reductions to better align resources with business levels. The reduction in hours worked by a portion of ABF Freight’s contractual employees resulted in lower contributions to multiemployer health and welfare plans for 2020. In 2021, more hours worked by ABF Freight’s contractual employees, as well as the hiring of additional contractual employees, primarily during the second half of 2021, to service higher shipment levels in response to increased customer demand resulted in an increase in contributions to multiemployer health and welfare plans in 2021, compared to 2020. 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 2021, 2020, and 2019 multiemployer health and welfare plan contributions.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
	Dec. 31, 2021
STOCKHOLDERS' EQUITY
STOCKHOLDERS' EQUITY	​ ​ NOTE K – STOCKHOLDERS’ EQUITY ​ Accumulated Other Comprehensive Income ​ Components of accumulated other comprehensive income were as follows at December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands) Pre-tax amounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net periodic benefit credit ​ $ 5,602 ​ $ 4,390 ​ $ 2,898 ​ Interest rate swap ​ ​ 419 ​ ​ (1,622) ​ ​ (563) ​ Foreign currency translation ​ (1,044) ​ (1,182) ​ (2,075) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ $ 4,977 ​ $ 1,586 ​ $ 260 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ After-tax amounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net periodic benefit credit ​ $ 4,160 ​ $ 3,260 ​ $ 2,152 ​ Interest rate swap ​ ​ 309 ​ ​ (1,198) ​ ​ (416) ​ Foreign currency translation ​ (770) ​ (872) ​ (1,533) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ $ 3,699 ​ $ 1,190 ​ $ 203 ​ ​ ​ The following is a summary of the changes in accumulated other comprehensive income (loss), net of tax, by component: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized ​ ​ Interest Foreign ​ ​ ​ ​ ​ ​ Net Periodic ​ ​ Rate ​ Currency ​ ​ Total Benefit Credit ​ Swap Translation ​ ​ ​ (in thousands) ​ Balances at December 31, 2019 ​ $ 203 ​ $ 2,152 ​ $ (416) ​ $ (1,533) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive income (loss) before reclassifications ​ 1,359 ​ 1,480 ​ ​ (782) ​ 661 ​ Amounts reclassified from accumulated other comprehensive income ​ (372) ​ (372) ​ ​ — ​ — ​ Net current-period other comprehensive income (loss) ​ 987 ​ 1,108 ​ ​ (782) ​ 661 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balances at December 31, 2020 ​ $ 1,190 ​ $ 3,260 ​ $ (1,198) ​ $ (872) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive loss before reclassifications ​ ​ 2,909 ​ ​ 1,300 ​ ​ 1,507 ​ ​ 102 ​ Amounts reclassified from accumulated other comprehensive income ​ ​ (400) ​ ​ (400) ​ ​ — ​ ​ — ​ Net current-period other comprehensive income ​ ​ 2,509 ​ ​ 900 ​ ​ 1,507 ​ ​ 102 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balances at December 31, 2021 ​ $ 3,699 ​ $ 4,160 ​ $ 309 ​ $ (770) ​ ​ ​ The following is a summary of the significant reclassifications out of accumulated other comprehensive income (loss) by component for the years ended December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized Net Periodic ​ ​ ​ Benefit Credit (1)(2) ​ 2021 2020 ​ ​ (in thousands) Amortization of net actuarial gain ​ $ 539 ​ $ 589 ​ Amortization of prior service credit ​ ​ — ​ 1 ​ Pension settlement expense (3) ​ ​ — ​ (89) ​ Total, pre-tax ​ ​ 539 ​ 501 ​ Tax expense ​ ​ (139) ​ (129) ​ Total, net of tax ​ $ 400 ​ $ 372 ​ (1) Amounts in parentheses indicate increases in expense or loss. (2) These components of accumulated other comprehensive income (loss) are included in the computation of net periodic benefit cost (see Note J). (3) Pension settlement expense is related to the supplemental benefit plan (see Note J). ​ Dividends on Common Stock ​ The following table is a summary of dividends declared during the applicable quarter: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 ​ ​ Per Share Amount Per Share Amount ​ ​ (in thousands, except per share data) First quarter ​ $ 0.08 ​ $ 2,037 ​ $ 0.08 ​ $ 2,033 ​ Second quarter ​ $ 0.08 ​ $ 2,058 ​ $ 0.08 ​ $ 2,049 ​ Third quarter ​ $ 0.08 ​ $ 2,050 ​ $ 0.08 ​ $ 2,040 ​ Fourth quarter ​ $ 0.08 ​ $ 1,994 ​ $ 0.08 ​ $ 2,035 ​ ​ On January 28, 2022, the Company’s Board of Directors declared a dividend of $0.08 per share payable to stockholders of record as of February 11, 2022. ​ Treasury Stock ​ The Company has a program to repurchase its common stock in the open market or in privately negotiated transactions (the “existing share repurchase program”). The existing 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 January 28, 2021, the Board of Directors extended the existing share repurchase program, making a total of $50.0 million available for purchases of the Company’s common stock. ​ On November 1, 2021, the Company announced that its Board of Directors authorized the Company to enter into an accelerated share repurchase program (“ASR”) and, on November 2, 2021, the Company entered into a fixed dollar ASR with a third-party financial institution to effect an accelerated repurchase of $100.0 million of the Company’s common stock. All share repurchase activities under the Company’s existing share repurchase program were suspended while the ASR was in effect. During 2021, the Company purchased 835,576 shares of its common stock for an aggregate cost of $83.1 million, of which 709,287 shares were repurchased under the ASR for an aggregate cost of $75.0 million. As of December 31, 2021, $66.9 million was available for repurchase under both the existing share repurchase program and the ASR. The remaining $25.0 million available under the ASR was recorded as an unsettled forward contract within stockholders’ equity as additional paid-in capital as of December 31, 2021. Treasury shares totaled 4,492,514 and 3,656,938 as of December 31, 2021 and 2020, respectively. ​ In January 2022, $25.0 million remaining under the ASR was settled with the repurchase of 214,763 shares. Immediately following final execution of the ASR, $41.9 million remained available under the existing share repurchase program. Subsequently, the Company has settled repurchases of 79,676 shares for an aggregate cost of $6.9 million under the existing share repurchase program as of February 25, 2022.

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2021
SHARE-BASED COMPENSATION
SHARE-BASED COMPENSATION	​ ​ NOTE L – 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, 2021 and 2020. 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, 2021 ​ 1,841,150 ​ $ 22.09 ​ Granted ​ 136,295 ​ $ 86.96 ​ Vested ​ (442,690) ​ $ 17.18 ​ Forfeited (1) ​ (52,356) ​ $ 29.59 ​ Outstanding – December 31, 2021 ​ 1,482,399 ​ $ 29.25 ​ (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 2021 136,295 ​ $ 86.96 ​ 2020 579,660 ​ $ 19.22 ​ 2019 386,840 ​ $ 27.75 ​ ​ The fair value of restricted stock awards that vested in 2021, 2020, and 2019 was $36.4 million, $7.8 million, and $4.9 million, respectively. Unrecognized compensation cost related to restricted stock awards outstanding as of December 31, 2021 was $16.9 million, which is expected to be recognized over a weighted-average period of approximately 1.4 years.

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
	Dec. 31, 2021
EARNINGS PER SHARE
EARNINGS PER SHARE	NOTE M – EARNINGS PER SHARE ​ The following table sets forth the computation of basic and diluted earnings per share for the years ended December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands, except share and per share data) Basic ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income ​ $ 213,521 ​ $ 71,100 ​ $ 39,985 ​ Effect of unvested restricted stock awards ​ — ​ — ​ (22) ​ Adjusted net income ​ $ 213,521 ​ $ 71,100 ​ $ 39,963 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares ​ 25,471,939 ​ 25,410,232 ​ 25,535,529 ​ Earnings per common share ​ $ 8.38 ​ $ 2.80 ​ $ 1.56 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income ​ $ 213,521 ​ $ 71,100 ​ $ 39,985 ​ Effect of unvested restricted stock awards ​ — ​ — ​ (21) ​ Adjusted net income ​ $ 213,521 ​ $ 71,100 ​ $ 39,964 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares ​ 25,471,939 ​ 25,410,232 ​ 25,535,529 ​ Effect of dilutive securities ​ 1,300,187 ​ 1,012,291 ​ 914,526 ​ Adjusted weighted-average shares and assumed conversions ​ 26,772,126 ​ 26,422,523 ​ 26,450,055 ​ Earnings per common share ​ $ 7.98 ​ $ 2.69 ​ $ 1.51 ​ ​ The Company used the two-class method of calculating earnings per share in 2019. Under the two-class method, dividends paid and a portion of undistributed net income, but not losses, are allocated to unvested RSUs that receive dividends, which are considered participating securities. Beginning with 2015 grants, the RSU agreements were modified to remove dividend rights and, therefore, the RSUs granted in 2021, 2020, and 2019 are not participating securities. During 2019, the remaining unvested RSUs receiving dividends became vested; therefore, the Company began using the treasury stock method for calculating earnings per share in 2020. ​ For the year ended December 31, 2019 outstanding stock awards of 0.2 million were not included in the diluted earnings per share calculations because their inclusion would have the effect of increasing the earnings per share.

OPERATING SEGMENT DATA

OPERATING SEGMENT DATA	12 Months Ended
	Dec. 31, 2021
OPERATING SEGMENT DATA
OPERATING SEGMENT DATA	NOTE N – 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, and key operating statistics to evaluate performance and allocate resources to the Company’s operations. ​ 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 also provides services to the ArcBest segment, including freight transportation related to certain consumer household goods self-move services. ​ ● The ArcBest segment includes the results of operations of the Company’s service offerings in ground expedite, truckload, dedicated, intermodal, household goods moving, managed transportation, warehousing and distribution, and international freight transportation for air, ocean, and ground. The ArcBest segment also provides services to the Asset-Based segment. ​ ● FleetNet includes the results of operations of FleetNet America, Inc. and certain other subsidiaries that provide roadside assistance and maintenance management services for commercial vehicles through a network of third-party service providers. FleetNet also provides services to the Asset-Based and ArcBest segments. ​ The Company’s other business activities and operating segments that are not reportable 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 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 operating segments are predominantly allocated based upon estimated and planned resource utilization-related metrics such as estimated shipment levels, number of pricing proposals, 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 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 for the years ended December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands) REVENUES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,573,773 ​ $ 2,092,031 ​ $ 2,144,679 ​ ArcBest (1) ​ 1,300,626 ​ 779,115 ​ 738,392 ​ FleetNet ​ 254,087 ​ 205,049 ​ 211,738 ​ Other and eliminations ​ (148,419) ​ (136,032) ​ (106,499) ​ Total consolidated revenues ​ $ 3,980,067 ​ $ 2,940,163 ​ $ 2,988,310 ​ OPERATING EXPENSES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Salaries, wages, and benefits ​ $ 1,198,253 ​ $ 1,095,694 ​ $ 1,148,761 ​ Fuel, supplies, and expenses ​ 266,139 ​ 209,095 ​ 257,133 ​ Operating taxes and licenses ​ 49,461 ​ 49,300 ​ 50,209 ​ Insurance ​ 37,800 ​ 33,568 ​ 32,516 ​ Communications and utilities ​ 18,773 ​ 17,916 ​ 18,614 ​ Depreciation and amortization ​ 93,799 ​ 94,326 ​ 89,798 ​ Rents and purchased transportation ​ 364,345 ​ 250,159 ​ 221,479 ​ Shared services ​ ​ 263,532 ​ ​ 217,258 ​ ​ 212,773 ​ Gain on sale of property and equipment (2) ​ (8,676) ​ (3,309) ​ (5,892) ​ Innovative technology costs (3) ​ ​ 27,631 ​ ​ 22,458 ​ ​ 13,739 ​ Other ​ 2,009 ​ 6,701 ​ 3,488 ​ Total Asset-Based ​ 2,313,066 ​ 1,993,166 ​ 2,042,618 ​ ArcBest (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Purchased transportation ​ 1,097,332 ​ 649,933 ​ 606,113 ​ Supplies and expenses ​ 10,531 ​ 9,627 ​ 10,789 ​ Depreciation and amortization ​ 11,387 ​ 9,714 ​ 11,344 ​ Shared services ​ ​ 132,137 ​ ​ 90,983 ​ ​ 93,961 ​ Gain on sale of subsidiaries (4) ​ ​ (6,923) ​ ​ — ​ ​ — ​ Other ​ ​ 9,765 ​ 9,203 ​ 9,860 ​ Asset impairment (5) ​ ​ — ​ ​ — ​ ​ 26,514 ​ Total ArcBest ​ 1,254,229 ​ 769,460 ​ 758,581 ​ FleetNet ​ 249,543 ​ 201,682 ​ 206,932 ​ Other and eliminations ​ (117,757) ​ (122,423) ​ (83,591) ​ Total consolidated operating expenses ​ $ 3,699,081 ​ $ 2,841,885 ​ $ 2,924,540 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ OPERATING INCOME ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 260,707 ​ $ 98,865 ​ $ 102,061 ​ ArcBest (1) ​ 46,397 ​ 9,655 ​ (20,189) ​ FleetNet ​ 4,544 ​ 3,367 ​ 4,806 ​ Other and eliminations ​ (30,662) ​ (13,609) ​ (22,908) ​ Total consolidated operating income ​ $ 280,986 ​ $ 98,278 ​ $ 63,770 ​ OTHER INCOME (COSTS) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest and dividend income ​ $ 1,275 ​ $ 3,616 ​ $ 6,453 ​ Interest and other related financing costs ​ (8,904) ​ (11,697) ​ (11,467) ​ Other, net (6) ​ 3,797 ​ 2,299 ​ (7,285) ​ Total other costs ​ (3,832) ​ (5,782) ​ (12,299) ​ INCOME BEFORE INCOME TAXES ​ $ 277,154 ​ $ 92,496 ​ $ 51,471 ​ (1) For 2021, includes the operations of MoLo since the November 1, 2021 acquisition (see Note D). (2) For 2021, includes an $8.6 million gain on the sale of unutilized service center property. (3) Represents costs associated with the freight handling pilot test program at ABF Freight. (4) Gain relates to the sale of the labor services portion of the ArcBest segment’s moving business in the second quarter 2021. (5) The ArcBest segment recognized a noncash impairment charge in 2019 related to a portion of the goodwill, customer relationship intangible assets, and revenue equipment associated with the acquisition of truckload and dedicated businesses within the segment (see Note E). (6) Includes the components of net periodic benefit cost other than service cost, including pension settlement and termination expense (see Note J), and proceeds and changes in cash surrender value of life insurance policies. ​ ​ The following table reflects information about revenues from customers and intersegment revenues: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands) Revenues from customers ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,470,529 ​ $ 1,998,549 ​ $ 2,077,287 ​ ArcBest ​ 1,291,679 ​ 770,560 ​ 731,366 ​ FleetNet ​ 213,882 ​ 166,654 ​ 175,055 ​ Other ​ 3,977 ​ 4,400 ​ 4,602 ​ Total consolidated revenues ​ $ 3,980,067 ​ $ 2,940,163 ​ $ 2,988,310 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Intersegment revenues ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 103,244 ​ $ 93,482 ​ $ 67,392 ​ ArcBest ​ ​ 8,947 ​ ​ 8,555 ​ ​ 7,026 ​ FleetNet ​ ​ 40,205 ​ ​ 38,395 ​ ​ 36,683 ​ Other and eliminations ​ ​ (152,396) ​ ​ (140,432) ​ ​ (111,101) ​ Total intersegment revenues ​ $ — ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total segment revenues ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,573,773 ​ ​ 2,092,031 ​ ​ 2,144,679 ​ ArcBest ​ ​ 1,300,626 ​ ​ 779,115 ​ ​ 738,392 ​ FleetNet ​ ​ 254,087 ​ ​ 205,049 ​ ​ 211,738 ​ Other and eliminations ​ ​ (148,419) ​ ​ (136,032) ​ ​ (106,499) ​ Total consolidated revenues ​ $ 3,980,067 ​ $ 2,940,163 ​ $ 2,988,310 ​ ​ The following table provides capital expenditure and depreciation and amortization information by reportable operating segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ 2021 2020 2019 ​ ​ ​ (in thousands) ​ CAPITAL EXPENDITURES, GROSS ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based (1) ​ $ 96,180 ​ $ 85,135 ​ $ 122,437 ​ ArcBest ​ ​ 9,565 ​ ​ 1,258 ​ ​ 3,909 ​ FleetNet ​ 1,174 ​ 675 ​ 590 ​ Other and eliminations (2)(3) ​ 11,193 ​ 17,983 ​ 33,748 ​ ​ ​ $ 118,112 ​ $ 105,051 ​ $ 160,684 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ ​ 2021 2020 2019 ​ ​ ​ (in thousands) ​ DEPRECIATION AND AMORTIZATION EXPENSE (2) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 93,799 ​ $ 94,326 ​ $ 89,798 ​ ArcBest (4) ​ ​ 11,387 ​ ​ 9,714 ​ ​ 11,344 ​ FleetNet (5) ​ 1,661 ​ 1,622 ​ 1,341 ​ Other and eliminations (2) ​ 17,374 ​ 12,729 ​ 9,983 ​ ​ ​ $ 124,221 ​ $ 118,391 ​ $ 112,466 ​ (1) Includes assets acquired through notes payable of $59.7 million, $61.8 million, and $67.6 million in 2021, 2020, and 2019, respectively. (2) Other and eliminations includes certain assets held for the benefit of multiple segments, including information systems equipment. 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 $23.2 million in 2019. (4) Includes amortization of intangibles of $5.3 million, $3.7 million, and $4.2 million in 2021, 2020, and 2019, respectively. (5) Includes amortization of intangibles which totaled less than $0.1 million in 2021 and $0.2 million in both 2020 and 2019. ​ 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 $32.8 million and $25.6 million for the year ended December 31, 2021 and 2020, respectively, related to innovative technology initiatives. ​ The following table presents operating expenses by category on a consolidated basis: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands) ​ OPERATING EXPENSES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Salaries, wages, and benefits ​ $ 1,550,859 ​ $ 1,368,588 ​ $ 1,408,409 ​ Rents, purchased transportation, and other costs of services ​ 1,570,050 ​ 974,835 ​ 934,958 ​ Fuel, supplies, and expenses ​ 324,380 ​ 250,221 ​ 316,047 ​ Depreciation and amortization (1) ​ 124,221 ​ 118,391 ​ 112,466 ​ Other (2) ​ 129,571 ​ 129,850 ​ 126,146 ​ Asset impairment (3) ​ ​ — ​ ​ — ​ ​ 26,514 ​ ​ ​ $ 3,699,081 ​ $ 2,841,885 ​ $ 2,924,540 ​ (1) Includes amortization of intangibles associated with acquired businesses. (2) The year ended December 31, 2021 includes a $6.9 million gain related to the sale of a subsidiary within the ArcBest segment and an $8.6 million gain related to the sale of an unutilized service center property within the Asset-Based segment. (3) The ArcBest segment recognized a noncash impairment charge in 2019 related to a portion of the goodwill, customer relationship intangible assets, and revenue equipment associated with the acquisition of truckload and dedicated businesses within the segment (see Note E). ​ ​

LEGAL PROCEEDINGS, ENVIRONMENTA

LEGAL PROCEEDINGS, ENVIRONMENTAL MATTERS, AND OTHER EVENTS	12 Months Ended
	Dec. 31, 2021
LEGAL PROCEEDINGS, ENVIRONMENTAL MATTERS, AND OTHER EVENTS
LEGAL PROCEEDINGS, ENVIRONMENTAL MATTERS, AND OTHER EVENTS	NOTE O – 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. ​ 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, 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 an accrual, which is included in 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. ​ Certain Asset-Based service center facilities operate with no exposure certifications or stormwater permits under the federal Clean Water Act (the “CWA”). The no exposure certification and stormwater permits may require periodic facility inspections and monitoring and reporting of stormwater sampling results. The Company determined that certain procedures regarding sampling, documentation, and reporting were not appropriately being performed in accordance with the CWA. As such, the Company self-reported the matter to the EPA. An estimated settlement expense for this matter is accrued within accrued expenses in the consolidated balance sheet as of December 31, 2021. Resolution of this matter is not expected to have a material adverse effect on the Company’s financial condition, results of operations, or cash flows. ​ Other Events ​ In February 2021, the Company received a Notice of Assessment from a state pertaining to uncollected sales and use tax, including interest and penalties, for the period September 1, 2016 to November 30, 2018. The Company does not agree with the basis of the assessment and filed an appeal in May 2021. The Company has previously accrued an amount related to this assessment 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. ​

SCHEDULE II - VALUATION AND QUA

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES	12 Months Ended
	Dec. 31, 2021
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 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deducted from asset accounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance for credit losses and revenue adjustments ​ $ 7,851 ​ $ 1,466 ​ $ 7,788 (a)(b) $ 3,879 (c) $ 13,226 ​ Allowance for other accounts receivable ​ $ 660 ​ $ 30 (d) $ — ​ $ — ​ $ 690 ​ Allowance for deferred tax assets ​ $ 1,284 ​ $ — ​ $ — ​ $ (912) (e) $ 2,196 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deducted from asset accounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance for credit losses and revenue adjustments ​ $ 5,448 ​ $ 4,327 ​ $ 1,887 (b) $ 3,811 (c) $ 7,851 ​ Allowance for other accounts receivable ​ $ 476 ​ $ (14) (d) $ 198 (f) $ — ​ $ 660 ​ Allowance for deferred tax assets ​ $ 668 ​ $ — ​ $ — ​ $ (616) (e) $ 1,284 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deducted from asset accounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Allowance for credit losses and revenue adjustments ​ $ 7,380 ​ $ 1,223 ​ $ (245) (b) $ 2,910 (c) $ 5,448 ​ Allowance for other accounts receivable ​ $ 806 ​ $ (330) (d) $ — ​ $ — ​ $ 476 ​ Allowance for deferred tax assets ​ $ 53 ​ $ — ​ $ — ​ $ (615) (e) $ 668 ​ ​ (a) Includes allowance assumed in the acquisition of MoLo Solutions, LLC. (See Note D to the Company’s consolidated financial statements included in Part II, Item 8 of the Annual Report on Form 10-K). (b) Change in allowance due to recoveries of amounts previously written off and adjustment of revenue. (c) Uncollectible accounts written off. (d) Charged (credited) to workers’ compensation expense. (e) Increase in allowance due to changes in expectations of realization of certain federal and state net operating losses and federal and state deferred tax assets. (f) Charged to retained earnings as of January 1, 2020 due to the adoption of ASC Topic 326, Financial Instruments – Credit Losses.

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2021
ACCOUNTING POLICIES
Consolidation	Consolidation:
Segment Information	Segment Information:
Use of Estimates	Use of Estimates:
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 earnings.
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 4% of its revenues in 2021, 2020, or 2019 or more than 7% of its accounts receivable balance at December 31, 2021 and 2020. The Company performs ongoing credit evaluations of its customers and generally does not require collateral. Historically, credit losses have been within management’s expectations.
Allowances	Allowances: ​
Property, Plant and Equipment, Including Repairs and Maintenance	Property, Plant and Equipment, Including Repairs and Maintenance: Purchases of property, plant and equipment are recorded at cost. For financial reporting purposes, property, plant and equipment is depreciated principally by the straight-line method, using the following useful lives: structures – primarily 15 to 60 years ; revenue equipment – 3 to 16 years ; and other equipment – 2 to 15 years . The Company utilizes tractors and trailers in its operations. Tractors and trailers are commonly referred to as “revenue equipment” in the transportation business. The Company periodically reviews and adjusts, as appropriate, the residual values and useful lives of revenue equipment and other equipment. For tax reporting purposes, accelerated depreciation or cost recovery methods are used. Gains and losses on asset sales are reflected in the year of disposal. Exchanges of nonmonetary assets that have commercial substance are measured based on the fair value of the assets exchanged. Tires purchased with revenue equipment are capitalized as a part of the cost of such equipment, with replacement tires being expensed when placed in service. Repair and maintenance costs associated with property, plant and equipment are expensed as incurred if the costs do not extend the useful life of the asset. If such costs do extend the useful life of the asset, the costs are capitalized and depreciated over the appropriate remaining useful life.
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: The Company capitalizes the costs of software acquired from third parties and qualifying internal computer software costs incurred during the application development stage, or during the implementation stage for cloud computing or hosting arrangements. Costs incurred in the preliminary project stage and postimplementation-operation stage, which includes maintenance and training costs, are expensed as incurred. For financial reporting purposes, capitalized software costs are amortized by the 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 $0.6 million and $1.1 million are reported within other noncurrent assets as of December 31, 2021 and 2020, respectively.
Business Combinations	Business Combinations: ​ On November 1, 2021, the Company acquired MoLo Solutions, LLC (“MoLo”), a Chicago-based truckload freight brokerage company. Terms of the transaction included initial consideration paid at closing of $239.4 million, subject to certain post-closing adjustments which were estimated at closing and will be finalized post-closing, and the potential for additional cash consideration based on achievement of certain targets of adjusted earnings before interest, taxes, depreciation, and amortization as adjusted for certain items pursuant to the merger agreement for years 2023 through 2025 (see Note D). ​
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 assesses qualitative factors to determine if it is more likely than not that the fair value of indefinite-lived intangible assets is less than its carrying value and performs a quantitative analysis 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.
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	Nonunion Defined Benefit Pension, Supplemental Benefit, and Postretirement Health Benefit Plans: ​ The Company recognizes the funded status of the supplemental benefit plan (the “SBP”) and postretirement health benefit plan in the consolidated balance sheet and recognizes changes in the funded status, net of tax, in the year in which they occur as a component of other comprehensive income or loss. The benefit obligations of the SBP and postretirement health benefit plan represent the funded status, as these plans do not have plan assets. Amounts recognized in other comprehensive income or loss are subsequently expensed as components of net periodic benefit cost by amortizing unrecognized net actuarial losses over the average remaining 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 nonunion defined benefit pension plan or the SBP since the accrual of benefits under the plans was frozen on July 1, 2013 and December 31, 2009, respectively; 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 (including pension settlement expense) of the nonunion defined benefit pension plan, the SBP, and the postretirement health benefit plan are reported within the other line item of other income (costs). ​ The expense and liability related to the SBP and postretirement health benefit plan, and, prior to termination, the nonunion defined benefit pension plan, are measured based upon a number of assumptions and using the services of a third-party actuary. The discount rates used to discount the plans’ obligations are determined by matching projected cash distributions with appropriate high-quality corporate bond yields in a yield curve analysis. Prior to plan termination, the Company established the expected rate of return on plan assets for the nonunion defined benefit pension plan by considering the historical and expected returns for the plan’s current investment mix. Assumptions are also made regarding expected retirement age, mortality, employee turnover, and, for the postretirement health benefit plan, future increases in health care costs. The assumptions used directly impact the net periodic benefit cost 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 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. ​ The Company uses December 31 as the measurement date for the SBP, postretirement health benefit plan, and, prior to termination, the nonunion defined benefit pension plan. Plan obligations are also remeasured upon curtailment and upon settlement. ​ The Company recorded quarterly pension settlement expense related to the nonunion defined benefit pension plan when qualifying distributions determined to be settlements were expected to exceed the estimated total annual interest cost of the plan. Benefit distributions under the SBP individually exceed the annual interest cost of the plan, and 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. Pension settlement expense for the nonunion defined benefit pension plan and SBP is presented in Note J.
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. Revenue adjustments may also occur due to rating or other billing adjustments. The Company estimates revenue adjustments based on historical information and revenue is recognized accordingly at the time of shipment. 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. ​ ArcBest Segment ArcBest segment revenues consist primarily of asset-light logistics services using third-party vendors to provide transportation services. ArcBest 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. ​ FleetNet Segment FleetNet segment revenues consist of service fee revenue, roadside repair revenue and routine maintenance services revenue. Service fee revenue for the FleetNet segment is recognized upon response to the service event. Repair and routine maintenance service revenue for the FleetNet segment is recognized upon completion of the service by third-party vendors. Revenue and expense from repair and maintenance services performed by third-party vendors are reported on a gross basis as FleetNet controls the services prior to transfer to the customer and remains primarily responsible to the customer for completion of the services. ​ 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: ​ Effective in 2020, the Company no longer had equity awards that were deemed participating securities. Basic earnings per share is calculated by dividing net income by the daily weighted number of shares of the Company’s common stock outstanding for the period. Diluted earnings per share is calculated using the treasury stock method. Under this method, the denominator used in calculating diluted earnings per share includes the impact of unvested restricted equity awards. ​
Share-Based Compensation	Share-Based Compensation: The fair value of restricted stock awards is determined based upon the closing market price of the Company’s common stock on the date of grant. The restricted stock units (“RSUs”) generally vest at the end of a five-year period following the date of grant for RSUs awarded prior to 2018, at the end of a four-year period following the date of grant for RSUs awarded in 2018 through 2020, and at the end of a three-year period following the date of grant for subsequent awards. Awards granted to non-employee directors typically vest at the end of a one-year period, subject to accelerated vesting due to death, disability, retirement, or change-in-control provisions. When RSUs become vested, the Company issues new shares which are subsequently distributed. Effective in 2020, the Company no longer had equity awards which were paid dividends or dividend equivalents during the vesting period. The Company recognizes the income tax benefits of dividends on share-based payment awards as income tax expense or benefit in the consolidated statements of operations when awards vest or are settled. ​ 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:
Adopted Accounting Pronouncements and Accounting Pronouncements Not Yet Adopted	Adopted Accounting Pronouncements ​ ASC Topic 740, Income Taxes, ​ Accounting Pronouncements Not Yet Adopted ​ Management believes there is no new accounting guidance issued but not yet effective that would have a material impact to the Company’s current financial statements.

FINANCIAL INSTRUMENTS AND FAI_2

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Dec. 31, 2021
FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS
Schedule components of cash and cash equivalents, short term investments, and restricted funds	​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 December 31 ​ ​ 2021 ​ 2020 ​ ​ (in thousands) ​ Cash and cash equivalents ​ ​ ​ ​ ​ ​ ​ Cash deposits (1) ​ $ 72,790 ​ $ 240,687 ​ Variable rate demand notes (1)(2) ​ 230 ​ 29,066 ​ Money market funds (3) ​ 3,600 ​ 34,201 ​ Total cash and cash equivalents ​ $ 76,620 ​ $ 303,954 ​ ​ ​ ​ ​ ​ ​ ​ ​ Short-term investments ​ ​ ​ ​ ​ ​ ​ Certificates of deposit (1) ​ $ 48,339 ​ $ 53,297 ​ U.S. Treasury securities (4) ​ ​ — ​ ​ 12,111 ​ Total short-term investments ​ $ 48,339 ​ $ 65,408 ​ (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	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 ​ ​ (in thousands) ​ ​ ​ ​ Carrying ​ Fair ​ Carrying ​ Fair ​ ​ ​ ​ Value ​ Value ​ Value ​ Value ​ Credit Facility (1) ​ $ 50,000 ​ $ 50,000 ​ $ 70,000 ​ $ 70,000 ​ Notes payable (2) ​ 175,530 ​ 175,937 ​ 214,216 ​ 217,226 ​ New England Pension Fund withdrawal liability (3) ​ ​ 20,769 ​ ​ 23,521 ​ ​ 21,407 ​ ​ 25,523 ​ ​ ​ $ 246,299 ​ $ 249,458 ​ $ 305,623 ​ $ 312,749 ​ (1) The revolving credit facility (the “Credit Facility”) carries a variable interest rate based on LIBOR, plus a margin, that is considered to be 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 3.1% and 2.6% at December 31, 2021 and 2020, respectively, determined using the 20-year U.S. Treasury rate plus a spread (Level 2 of the fair value hierarchy). As of December 31, 2021, the outstanding withdrawal liability totaled $20.8 million, of which $0.7 million and $20.1 million was recorded in accrued expenses and other long-term liabilities, respectively. ​
Schedule of financial assets and liabilities measured at fair value on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ ​ ​ ​ ​ ​ 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) ​ $ 3,600 ​ $ 3,600 ​ $ — ​ $ — ​ Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan (2) ​ 3,848 ​ 3,848 ​ — ​ — ​ Interest rate swaps (3) ​ ​ 874 ​ ​ — ​ ​ 874 ​ ​ — ​ ​ ​ $ 8,322 ​ $ 7,448 ​ $ 874 ​ $ — ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps (3) ​ $ 455 ​ $ — ​ $ 455 ​ $ — ​ Contingent consideration (4) ​ ​ 93,700 ​ ​ — ​ ​ — ​ ​ 93,700 ​ ​ ​ $ 94,155 ​ $ — ​ $ 455 ​ $ 93,700 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ 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) ​ $ 34,201 ​ $ 34,201 ​ $ — ​ $ — ​ Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan (2) ​ 2,955 ​ 2,955 ​ — ​ — ​ ​ ​ $ 37,156 ​ $ 37,156 ​ $ — ​ $ — ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swaps (3) ​ $ 1,622 ​ $ — ​ $ 1,622 ​ $ — ​ ​ ​ (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 or other long-term liabilities. The fair values of the interest rate swaps were 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, 2021 and 2020 and considers the interest rate swap valuations in Level 2 of the fair value hierarchy. (4) Included in other long-term liabilities, based on when expected payouts become due. The estimated fair value of contingent consideration for an earn-out agreement related to the November 2021 acquisition of MoLo was determined by assessing Level 3 inputs. The Level 3 assessments utilize a Monte Carlo simulation with inputs including scenarios of estimated revenues and earnings before interest, taxes, depreciation and amortization to be achieved for the applicable performance periods, volatility factors applied to the simulations, and the discount rate applied, which was 9.0% as of December 2021. A 100 basis point decrease in the discount rate would increase the liability by $4.2 million. Subsequent changes to fair value as a result of recurring assessments will be recognized in operating income.

ACQUISITION (Tables)

ACQUISITION (Tables)	12 Months Ended
	Dec. 31, 2021
ACQUISITION.
Schedule of purchase consideration and estimated fair values of the acquired assets and liabilities	​ ​ ​ ​ ​ ​ ​ ​ Purchase ​ ​ ​ Consideration ​ ​ ​ (in thousands) ​ Net cash consideration, including estimated post-closing adjustments ​ $ 239,398 ​ Contingent consideration ​ ​ 93,700 ​ Total purchase consideration ​ $ 333,098 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Purchase ​ Allocation ​ ​ (in thousands) Accounts receivable, less allowances ​ $ 136,522 ​ Prepaid expenses ​ 766 ​ Property and equipment, net ​ 2,309 ​ Operating lease right-of-use assets ​ 844 ​ Intangible assets ​ 76,900 ​ Other assets ​ 323 ​ Total identifiable assets acquired ​ 217,664 ​ ​ ​ ​ ​ ​ Accounts payable ​ 94,909 ​ Accrued expenses and other current liabilities ​ 2,643 ​ Operating lease liabilities ​ 983 ​ Total liabilities ​ 98,535 ​ ​ ​ ​ ​ ​ Total identifiable net assets ​ 119,129 ​ Goodwill ​ 213,969 ​ Net assets acquired ​ $ 333,098 ​ ​
Schedule of pro forma supplemental information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31 ​ ​ 2021 2020 ​ ​ (Unaudited) ​ ​ ​ (in thousands, except per share data) ​ ​ ​ ​ ​ ​ ​ ​ Revenues $ 4,488,564 ​ $ 3,213,722 ​ Income before income taxes ​ $ 266,866 ​ $ 63,622 ​ Net income ​ $ 205,728 ​ $ 48,290 ​ Diluted EPS ​ $ 7.68 ​ $ 1.83 ​

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2021
GOODWILL AND INTANGIBLE ASSETS
Schedule of goodwill by reportable operating segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ArcBest FleetNet ​ ​ (in thousands) Balances at December 31, 2019 and 2020 ​ $ 88,320 ​ $ 87,690 ​ $ 630 ​ Goodwill acquired (1) ​ 213,969 ​ 213,969 ​ ​ — ​ Goodwill divested (2) ​ ​ (1,952) ​ ​ (1,952) ​ ​ — ​ Balances at December 31, 2021 ​ $ 300,337 ​ $ 299,707 ​ $ 630 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated impairment at December 31, 2021 ​ $ (20,000) ​ $ (20,000) ​ $ — ​ (1) Goodwill acquired relates to the acquisition of MoLo (see Note D). (2) Goodwill divested due to the sale of the labor services portion of the ArcBest segment’s moving business in second quarter 2021 was determined based on the relative fair value of the business sold to the total fair value of the reporting unit.
Schedule of intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 ​ ​ 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 ​ $ 100,321 ​ $ 35,072 ​ $ 65,249 ​ $ 52,721 ​ $ 30,477 ​ $ 22,244 ​ Other ​ 8 ​ ​ 30,335 ​ ​ 1,304 ​ ​ 29,031 ​ ​ 980 ​ ​ 543 ​ ​ 437 ​ ​ 11 ​ 130,656 ​ 36,376 ​ 94,280 ​ ​ 53,701 ​ 31,020 ​ 22,681 ​ Indefinite-lived intangible assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Trade name N/A ​ 32,300 ​ N/A ​ 32,300 ​ ​ 32,300 ​ N/A ​ 32,300 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total intangible assets N/A ​ $ 162,956 ​ $ 36,376 ​ $ 126,580 ​ $ 86,001 ​ $ 31,020 ​ $ 54,981 ​
Schedule of future amortization for intangible assets	​ ​ ​ ​ ​ ​ ​ Amortization of ​ ​ Intangible Assets ​ ​ (in thousands) ​ 2022 ​ $ 12,920 ​ 2023 ​ 12,826 ​ 2024 ​ 12,793 ​ 2025 ​ 12,778 ​ 2026 ​ ​ 8,671 ​ Thereafter ​ ​ 34,292 ​ Total amortization ​ $ 94,280 ​

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2021
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: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands) Current provision: ​ ​ ​ ​ Federal ​ $ 56,451 ​ $ 10,001 ​ $ 2,202 ​ State ​ 14,430 ​ 3,267 ​ 1,813 ​ Foreign ​ 341 ​ 413 ​ 2,060 ​ ​ ​ 71,222 ​ 13,681 ​ 6,075 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred provision (benefit): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Federal ​ (6,098) ​ 5,948 ​ 4,196 ​ State ​ (1,554) ​ 1,789 ​ 1,221 ​ Foreign ​ 63 ​ (22) ​ (6) ​ ​ ​ (7,589) ​ 7,715 ​ 5,411 ​ Total provision for income taxes ​ $ 63,633 ​ $ 21,396 ​ $ 11,486 ​
Schedule of components of the deferred tax provision or benefit	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 ​ 2019 ​ ​ (in thousands) Amortization, depreciation, and basis differences for property, plant and equipment and other long-lived assets (1) $ 1,451 $ 4,975 $ 16,255 ​ Amortization of intangibles and impairment ​ (536) ​ 183 ​ (6,933) ​ Changes in reserves for workers’ compensation, third-party casualty, and cargo claims ​ (3,294) ​ (182) ​ (1,880) ​ Revenue recognition ​ (1,445) ​ (1,481) ​ (1,437) ​ Allowance for credit losses ​ 156 ​ (652) ​ 541 ​ Nonunion pension and other retirement plans ​ (3) ​ 957 ​ 564 ​ Multiemployer pension fund withdrawal ​ ​ 164 ​ ​ 157 ​ ​ 150 ​ Federal and state net operating loss carryforwards utilized (generated) ​ (300) ​ (259) ​ 59 ​ State depreciation adjustments ​ 598 ​ 343 ​ (1,302) ​ Share-based compensation ​ (984) ​ (195) ​ (709) ​ Valuation allowance increase ​ 911 ​ 617 ​ 383 ​ Other accrued expenses ​ (4,097) ​ 1,663 ​ (699) ​ Prepaid expenses ​ ​ (788) ​ ​ 1,207 ​ ​ 1,782 ​ Operating lease right-of-use assets/liabilities – net ​ ​ (228) ​ ​ (13) ​ ​ (1,049) ​ Other ​ 806 ​ 395 ​ (314) ​ Deferred tax provision (benefit) ​ $ (7,589) ​ $ 7,715 ​ $ 5,411 ​ (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 a decrease in the purchase of assets eligible for 100% depreciation, the deferred tax expense related to the tax depreciation expense in excess of book depreciation decreased over the three-year period from 2019 through 2021.
Schedule of significant components of deferred tax assets and liabilities	Significant components of the deferred tax assets and liabilities at December 31 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 ​ ​ (in thousands) Deferred tax assets: ​ ​ ​ Accrued expenses ​ $ 47,683 ​ $ 40,502 ​ Operating lease liabilities ​ ​ 30,590 ​ ​ 33,933 ​ Supplemental pension liabilities ​ ​ 97 ​ ​ 103 ​ Multiemployer pension fund withdrawal ​ ​ 5,247 ​ ​ 5,409 ​ Postretirement liabilities other than pensions ​ 4,441 ​ 4,871 ​ Share-based compensation ​ 6,755 ​ 5,827 ​ Federal and state net operating loss carryovers ​ 1,652 ​ 1,353 ​ Revenue recognition ​ ​ 2,778 ​ ​ 1,426 ​ Other ​ 266 ​ 1,297 ​ Total deferred tax assets ​ 99,509 ​ 94,721 ​ Valuation allowance ​ (2,196) ​ (1,284) ​ Total deferred tax assets, net of valuation allowance ​ 97,313 ​ 93,437 ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ ​ Amortization, depreciation, and basis differences for property, plant and equipment, and other long-lived assets ​ 114,999 ​ 113,092 ​ Operating lease right-of-use assets ​ ​ 29,403 ​ ​ 32,923 ​ Intangibles ​ 6,966 ​ 7,520 ​ Prepaid expenses ​ 5,368 ​ 6,151 ​ Total deferred tax liabilities ​ 156,736 ​ 159,686 ​ Net deferred tax liabilities ​ $ (59,423) ​ $ (66,249) ​ ​
Reconciliation between the effective income tax rate, as computed on income or loss before income taxes, and the statutory federal income tax rate	Reconciliation between the effective income tax rate, as computed on income before income taxes, and the statutory federal income tax rate for the years ended December 31 is presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 ​ 2019 ​ ​ (in thousands, except percentages) Income tax provision at the statutory federal rate of 21.0% $ 58,202 $ 19,424 $ 10,809 ​ Federal income tax effects of: ​ ​ ​ ​ ​ ​ ​ ​ ​ State income taxes ​ (2,704) ​ (1,062) ​ (637) ​ Nondeductible expenses ​ 3,596 ​ 1,395 ​ 1,344 ​ Life insurance proceeds and changes in cash surrender value ​ (866) ​ (488) ​ (775) ​ Alternative fuel credit ​ — ​ (1,261) ​ (2,340) ​ Net increase in valuation allowances ​ 887 ​ 617 ​ 382 ​ Net increase (decrease) in uncertain tax positions ​ ​ 854 ​ ​ (933) ​ ​ (20) ​ Settlement of share-based compensation ​ ​ (6,140) ​ ​ 420 ​ ​ 388 ​ Nonunion pension termination expense ​ ​ — ​ ​ — ​ ​ 1,040 ​ Foreign tax credits generated ​ ​ (404) ​ ​ (391) ​ ​ (2,054) ​ Federal research and development tax credits ​ ​ (2,044) ​ ​ (2,078) ​ ​ (1,354) ​ Other ​ (1,028) ​ 306 ​ (385) ​ Federal income tax provision ​ 50,353 ​ 15,949 ​ 6,398 ​ State income tax provision ​ 12,876 ​ 5,056 ​ 3,034 ​ Foreign income tax provision ​ 404 ​ 391 ​ 2,054 ​ Total provision for income taxes ​ $ 63,633 ​ $ 21,396 ​ $ 11,486 ​ Effective tax rate ​ 23.0 % 23.1 % 22.3 % ​

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2021
LEASES
Schedule of components of lease expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31 ​ 2021 2020 2019 ​ ​ (in thousands) Operating lease expense ​ $ 26,552 ​ $ 24,559 ​ $ 22,291 Variable lease expense ​ ​ 4,128 ​ ​ 3,152 ​ ​ 3,366 Sublease income ​ ​ (626) ​ ​ (398) ​ ​ (324) Total operating lease expense (1) ​ $ 30,054 ​ $ 27,313 ​ $ 25,333 (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 ​ ​ ​ 2021 ​ 2020 2019 ​ ​ ​ (in thousands) ​ Noncash change in operating right-of-use assets ​ $ 24,023 ​ $ 21,184 ​ $ 20,439 ​ Change in operating lease liabilities ​ ​ (23,400) ​ ​ (20,428) ​ ​ (19,711) ​ Operating right-of-use-assets and lease liabilities, net ​ $ 623 ​ $ 756 ​ $ 728 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid for amounts included in the measurement of operating lease liabilities ​ $ (25,909) ​ $ (23,810) ​ $ (21,714) ​
Schedule of supplemental balance sheet information related to lease liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ ​ (in thousands, except lease term and discount rate) ​ ​ ​ ​ ​ Land and ​ Equipment ​ ​ ​ Total ​ Structures ​ and Others Operating right-of-use assets (long-term) ​ $ 106,686 ​ $ 106,394 ​ $ 292 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease liabilities (current) ​ $ 22,740 ​ $ 22,477 ​ $ 263 Operating lease liabilities (long-term) ​ 88,835 ​ ​ 88,810 ​ ​ 25 Total operating lease liabilities ​ $ 111,575 ​ $ 111,287 ​ $ 288 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term (in years) ​ ​ 6.9 ​ ​ ​ ​ ​ ​ Weighted-average discount rate ​ ​ 2.88% ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ (in thousands, except lease term and discount rate) ​ ​ ​ ​ ​ ​ Land and ​ Equipment ​ ​ ​ ​ Total ​ Structures ​ and Others ​ Operating right-of-use assets (long-term) ​ $ 115,195 ​ $ 114,908 ​ $ 287 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating lease liabilities (current) ​ $ 21,482 ​ $ 21,207 ​ $ 275 ​ Operating lease liabilities (long-term) ​ 97,839 ​ ​ 97,828 ​ ​ 11 ​ Total operating lease liabilities ​ $ 119,321 ​ $ 119,035 ​ $ 286 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average remaining lease term (in years) ​ ​ 6.7 ​ ​ ​ ​ ​ ​ ​ Weighted-average discount rate ​ ​ 3.18% ​ ​ ​ ​ ​ ​ ​
Schedule of maturities of operating lease liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equipment ​ ​ ​ ​ ​ ​ Land and ​ and ​ ​ Total Structures (1) Other ​ (in thousands) ​ 2022 ​ $ 25,567 ​ $ 25,302 ​ $ 265 ​ 2023 ​ 19,800 ​ 19,775 ​ 25 ​ 2024 ​ 17,414 ​ 17,414 ​ — ​ 2025 ​ 14,839 ​ 14,839 ​ — ​ 2026 ​ 11,404 ​ 11,404 ​ — ​ Thereafter ​ 33,750 ​ 33,750 ​ — ​ Total lease payments ​ ​ 122,774 ​ ​ 122,484 ​ ​ 290 ​ Less imputed interest ​ ​ (11,199) ​ ​ (11,197) ​ ​ (2) ​ Total ​ $ 111,575 ​ $ 111,287 ​ $ 288 ​ ​ (1) Excludes future minimum lease payments for leases which were executed but had not yet commenced as of December 31, 2021 of $85.3 million which will be paid over 10 - 12 years . The Company plans to take possession of the leased spaces during 2022 .

LONG-TERM DEBT AND FINANCING _2

LONG-TERM DEBT AND FINANCING ARRANGEMENTS (Tables)	12 Months Ended
	Dec. 31, 2021
LONG-TERM DEBT AND FINANCING ARRANGEMENTS
Schedule of long-term debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 ​ December 31 ​ ​ 2021 2020 ​ ​ (in thousands) ​ Credit Facility (interest rate of 1.2% (1) ​ $ 50,000 ​ $ 70,000 ​ Notes payable (weighted-average interest rate of 2.4% at December 31, 2021) ​ 175,530 ​ 214,216 ​ Finance lease obligations (weighted-average interest rate of 3.3% at December 31, 2021) ​ 2 ​ 8 ​ ​ ​ 225,532 ​ 284,224 ​ Less current portion ​ 50,615 ​ 67,105 ​ Long-term debt, less current portion ​ $ 174,917 ​ $ 217,119 ​ (1) The interest rate swap mitigates interest rate risk by effectively converting $50.0 million of borrowings under the Credit Facility from variable-rate interest to fixed-rate interest with a per annum rate of 3.12% based on the margin of the Credit Facility as of December 31, 2021 and 2020.
Scheduled maturities of long-term debt obligations	Scheduled maturities of long term debt obligations as of December 31, 2021 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Credit Notes Finance Lease ​ ​ ​ Total ​ Facility (1) ​ Payable ​ Obligations ​ ​ ​ (in thousands) ​ 2022 ​ $ 55,060 ​ $ 807 ​ $ 54,251 ​ $ 2 ​ 2023 ​ 51,599 ​ 1,213 ​ ​ 50,386 ​ — ​ 2024 ​ 95,675 ​ 51,028 ​ ​ 44,647 ​ — ​ 2025 ​ 22,856 ​ — ​ ​ 22,856 ​ — ​ 2026 ​ 10,898 ​ ​ — ​ ​ 10,898 ​ ​ — ​ Thereafter ​ 293 ​ ​ — ​ ​ 293 ​ ​ — ​ Total payments ​ 236,381 ​ 53,048 ​ ​ 183,331 ​ 2 ​ Less amounts representing interest ​ 10,849 ​ 3,048 ​ 7,801 ​ — ​ Long-term debt ​ $ 225,532 ​ $ 50,000 ​ $ 175,530 ​ $ 2 ​ (1) The future interest payments included in the scheduled maturities due are calculated using variable interest rates based on the LIBOR swap curve, plus the anticipated applicable margin. ​ ​
Schedule of assets securing notes payable or held under capital leases	Assets securing notes payable or held under finance leases at December 31 were included in property, plant and equipment as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 ​ December 31 ​ ​ 2021 2020 ​ ​ (in thousands) Revenue equipment $ 241,892 $ 326,823 ​ Service, office, and other equipment ​ ​ 29,773 ​ ​ 26,270 ​ Total assets securing notes payable or held under finance leases ​ 271,665 ​ 353,093 ​ Less accumulated depreciation and amortization (1) ​ 88,696 ​ 115,424 ​ Net assets securing notes payable or held under finance leases ​ $ 182,969 ​ $ 237,669 ​ (1) Amortization of assets held under finance leases and depreciation of assets securing notes payable are included in depreciation expense .

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	12 Months Ended
	Dec. 31, 2021
ACCRUED EXPENSES.
Schedule of accrued expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31 ​ ​ 2021 2020 ​ ​ ​ (in thousands) ​ Workers’ compensation, third-party casualty, and loss and damage claims reserves ​ $ 116,535 ​ $ 103,898 ​ Accrued vacation pay ​ 52,746 ​ 51,728 ​ Accrued compensation, including retirement benefits ​ ​ 110,755 ​ ​ 67,690 ​ Taxes other than income ​ 10,225 ​ 10,468 ​ Other ​ 15,590 ​ 12,962 ​ Total accrued expenses ​ $ 305,851 ​ $ 246,746 ​

EMPLOYEE BENEFIT PLANS (Tables)

EMPLOYEE BENEFIT PLANS (Tables)	12 Months Ended
	Dec. 31, 2021
EMPLOYEE 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 ​ 2021 2020 2021 2020 ​ ​ (in thousands) Change in benefit obligations ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Benefit obligations, beginning of year ​ $ 392 ​ $ 3,236 ​ $ 18,751 ​ $ 20,630 ​ Service cost ​ — ​ — ​ 192 ​ 187 ​ Interest cost ​ 4 ​ 9 ​ 427 ​ 576 ​ Actuarial (gain) loss (1) ​ (15) ​ 34 ​ (1,736) ​ (2,027) ​ Benefits paid ​ — ​ (2,887) ​ (642) ​ (615) ​ Benefit obligations, end of year ​ 381 ​ 392 ​ 16,992 ​ 18,751 ​ Change in plan assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value of plan asset, beginning of year ​ — ​ — ​ — ​ — ​ Employer contributions ​ — ​ 2,887 ​ 642 ​ 615 ​ Benefits paid ​ — ​ (2,887) ​ (642) ​ (615) ​ Fair value of plan assets, end of year ​ — ​ — ​ — ​ — ​ Funded status at period end ​ $ (381) ​ $ (392) ​ $ (16,992) ​ $ (18,751) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated benefit obligation ​ $ 381 ​ $ 392 ​ $ 16,992 ​ $ 18,751 ​ (1) The actuarial gain on the postretirement health benefit plan for 2021 and 2020 is primarily related to the impact of actuarial assumptions on the valuation of plan costs. For 2021, these actuarial assumptions include an increase in the discount rate used to remeasure the plan obligation at December 31, 2021 versus December 31, 2020 and lower actual healthcare premium costs versus the assumed trend rates. For 2020, these actuarial assumptions include lower health care cost trend rates, partially offset by a decrease in the discount rate used to remeasure the plan obligation at December 31, 2020 versus December 31, 2019. ​
Schedule of amounts recognized in the consolidated balance sheets related to nonunion defined benefit plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental ​ Postretirement ​ ​ Benefit Plan ​ Health Benefit Plan ​ 2021 2020 2021 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current portion of pension and postretirement liabilities ​ $ — ​ $ — ​ $ (640) ​ $ (588) ​ Pension and postretirement liabilities, less current portion ​ (381) ​ (392) ​ (16,352) ​ (18,163) ​ Liabilities recognized ​ $ (381) ​ $ (392) ​ $ (16,992) ​ $ (18,751) ​ ​
Summary of the components of net periodic benefit cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nonunion Defined ​ Supplemental ​ Postretirement ​ ​ ​ Benefit Pension Plan ​ Benefit Plan ​ Health Benefit Plan ​ ​ 2021 2020 2019 2021 2020 2019 2021 2020 2019 ​ ​ (in thousands) ​ ​ ​ Service cost ​ $ — ​ $ — ​ $ — ​ $ — ​ $ — ​ $ — ​ $ 192 ​ $ 187 ​ $ 320 ​ Interest cost ​ — ​ — ​ 624 ​ 4 ​ 9 ​ 39 ​ 427 ​ 576 ​ 1,212 ​ Expected return on plan assets ​ ​ — ​ ​ — ​ ​ (31) ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ Amortization of prior service credit ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ (1) ​ ​ (33) ​ Pension settlement expense (1) ​ ​ — ​ ​ — ​ ​ 4,164 ​ ​ — ​ ​ 89 ​ ​ 370 ​ ​ — ​ ​ — ​ ​ — ​ Amortization of net actuarial (gain) loss (2) ​ — ​ — ​ 260 ​ 9 ​ 8 ​ 95 ​ (548) ​ (597) ​ 898 ​ Net periodic benefit cost ​ $ — ​ $ — ​ $ 5,017 ​ $ 13 ​ $ 106 ​ $ 504 ​ $ 71 ​ $ 165 ​ $ 2,397 ​ (1) For 2019, the presentation of pension settlement expense excludes a $4.0 million noncash pension termination expense which is further described within this Note. (2) 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.
Summary of pension settlement distributions and settlement expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nonunion Defined ​ Supplemental ​ ​ Benefit Pension Plan ​ Benefit Plan ​ 2021 2020 2019 (1) 2021 2020 (2) 2019 (3) ​ ​ (in thousands, except per share data) Pension settlement distributions ​ $ — ​ $ — ​ $ 33,938 ​ $ — ​ $ 2,887 ​ $ 937 ​ Pension settlement expense, pre-tax (4) ​ $ — ​ $ — ​ $ 4,164 ​ $ — ​ $ 89 ​ $ 370 ​ Pension settlement expense per diluted share, net of taxes ​ $ — ​ $ — ​ $ 0.12 ​ $ — ​ $ — ​ $ 0.01 ​ (1) Pension settlement distributions for 2019 represent $18.4 million of lump-sum benefit distributions, including participant-elected distributions associated with the plan’s termination, a $14.0 million nonparticipating annuity contract purchase, and a $1.5 million transfer of benefit obligations to the PBGC. (2) The 2020 SBP distributions include the portion of a benefit related to an officer retirement that occurred in 2019 which was delayed for six months after retirement in accordance with IRC Section 409A. (3) The 2019 SBP distribution excludes the portion of the benefit related to an officer retirement which was delayed for six months after retirement in accordance with IRC Section 409A. The pension settlement expense related to the delayed distribution was recognized in 2019. (4) For 2019, the presentation of pension settlement expense excludes a $4.0 million noncash pension termination expense which is further described within this Note. ​
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 ​ 2021 2020 2021 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net actuarial (gain) loss ​ $ 40 ​ $ 64 ​ $ (5,642) ​ $ (4,454) ​ ​
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 ​ 2021 2020 2021 2020 Discount rate ​ 1.8 % 1.1 % 2.7 % 2.3 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nonunion Defined ​ Supplemental ​ Postretirement ​ ​ Benefit Pension Plan ​ Benefit Plan ​ Health Benefit Plan ​ 2021 2020 2019 (1) 2021 2020 2019 2021 2020 2019 Discount rate ​ N/A ​ N/A ​ 3.9 % 1.1 % 2.4 % 3.6 % 2.3 % 3.1 % 4.2 % Expected return on plan assets ​ N/A ​ N/A ​ 1.4 % N/A N/A N/A N/A N/A N/A ​ (1) The discount rate presented was used to determine the first quarter 2019 expense, and the short-term discount rate established upon quarterly settlements in 2019 of 3.8% and 3.7% , was used to calculate the expense for the second and third quarter of 2019, respectively. The expected return on plan assets presented was used to determine nonunion pension expense for first quarter 2019, and no expected return on plan assets was assumed for the second and third quarters of 2019.
Schedule of the assumed health care cost trend rates for the postretirement health benefit plan	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 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 2033 2032 (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, 2021 and 2020 are for 2023 and 2022, respectively.
Schedule of estimated future benefit payments for nonunion defined benefit plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Supplemental Postretirement ​ ​ Benefit ​ Health ​ ​ Plan ​ Benefit Plan ​ ​ ​ ​ ​ ​ ​ 2022 ​ $ — ​ $ 640 ​ 2023 ​ $ — ​ $ 633 ​ 2024 ​ $ — ​ $ 584 ​ 2025 ​ $ — ​ $ 605 ​ 2026 ​ $ — ​ $ 642 ​ 2027-2031 ​ $ 424 ​ $ 3,522 ​ ​
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) 2021 2020 Implemented (c) 2021 2020 2019 Imposed (e) Central States, Southeast and Southwest Areas Pension Plan (1)(2) 36-6044243 Critical and Declining Critical and Declining Implemented (3) ​ $ 71,045 ​ $ 68,704 ​ $ 75,803 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Western Conference of Teamsters Pension Plan (2) 91-6145047 Green Green No ​ 25,861 ​ 23,633 ​ 24,860 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Central Pennsylvania Teamsters Defined Benefit Plan (1)(2) 23-6262789 Green Green No ​ 13,931 ​ 13,485 ​ 13,907 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ I. B. of T. Union Local No. 710 Pension Fund (5)(6) 36-2377656 Green (4) Green (4) No ​ 9,553 ​ 9,885 ​ 10,164 No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ New England Teamsters Pension Fund (7)(8) 04-6372430 Critical and Declining (9) Critical and Declining (9) Implemented (10) ​ 4,357 ​ 4,464 ​ 4,802 ​ No ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ All other plans in the aggregate ​ ​ ​ ​ ​ ​ ​ ​ ​ 22,146 ​ 22,023 ​ 24,210 ​ ​ Total multiemployer pension contributions paid (11) ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 146,893 ​ $ 142,194 ​ $ 153,746 ​ ​ 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 2021 and 2020 is for the plan’s year-end status at December 31, 2020 and 2019, 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. ​ (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, 2020 and 2019. (2) 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, 2020 and 2019. (3) Adopted a rehabilitation plan effective March 25, 2008 as updated. Utilized amortization extension granted by the IRS effective December 31, 2003. (4) PPA zone status relates to plan years February 1, 2020 – January 31, 2021 and February 1, 2019 – January 31, 2020. (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, 2020. (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, 2021 and 2020. (7) Contributions include $1.6 million for 2021, 2020, and 2019, respectively, 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 period of 23 years . (8) 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, 2020 and 2019. (9) PPA zone status relates to plan years October 1, 2020 – September 30, 2021 and October 1, 2019 – September 30, 2020. (10) Adopted a rehabilitation plan effective January 1, 2009. (11) 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 2018 ABF NMFA 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 business levels. Due to the negative impact of the COVID-19 pandemic on tonnage levels, most significantly in the second quarter of 2020, the Company made operational changes in the Asset-Based network in the second and third quarters of 2020, including workforce reductions to better align resources with business levels. The reduction in hours worked by a portion of ABF Freight’s contractual employees contributed to lower contributions to multiemployer pension plans for 2020. An increase in hours worked by ABF Freight’s contractual employees in 2021, as well as additional contractual employees hired primarily in the second half of the year, to service higher shipment levels in response to increased customer demand resulted in an increase in multiemployer pension contributions for 2021, compared to 2020.

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	12 Months Ended
	Dec. 31, 2021
STOCKHOLDERS' EQUITY
Components of accumulated other comprehensive income	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands) Pre-tax amounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net periodic benefit credit ​ $ 5,602 ​ $ 4,390 ​ $ 2,898 ​ Interest rate swap ​ ​ 419 ​ ​ (1,622) ​ ​ (563) ​ Foreign currency translation ​ (1,044) ​ (1,182) ​ (2,075) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ $ 4,977 ​ $ 1,586 ​ $ 260 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ After-tax amounts: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized net periodic benefit credit ​ $ 4,160 ​ $ 3,260 ​ $ 2,152 ​ Interest rate swap ​ ​ 309 ​ ​ (1,198) ​ ​ (416) ​ Foreign currency translation ​ (770) ​ (872) ​ (1,533) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total ​ $ 3,699 ​ $ 1,190 ​ $ 203 ​
Summary of changes in accumulated other comprehensive income (loss), net of tax, by component	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized ​ ​ Interest Foreign ​ ​ ​ ​ ​ ​ Net Periodic ​ ​ Rate ​ Currency ​ ​ Total Benefit Credit ​ Swap Translation ​ ​ ​ (in thousands) ​ Balances at December 31, 2019 ​ $ 203 ​ $ 2,152 ​ $ (416) ​ $ (1,533) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive income (loss) before reclassifications ​ 1,359 ​ 1,480 ​ ​ (782) ​ 661 ​ Amounts reclassified from accumulated other comprehensive income ​ (372) ​ (372) ​ ​ — ​ — ​ Net current-period other comprehensive income (loss) ​ 987 ​ 1,108 ​ ​ (782) ​ 661 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balances at December 31, 2020 ​ $ 1,190 ​ $ 3,260 ​ $ (1,198) ​ $ (872) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other comprehensive loss before reclassifications ​ ​ 2,909 ​ ​ 1,300 ​ ​ 1,507 ​ ​ 102 ​ Amounts reclassified from accumulated other comprehensive income ​ ​ (400) ​ ​ (400) ​ ​ — ​ ​ — ​ Net current-period other comprehensive income ​ ​ 2,509 ​ ​ 900 ​ ​ 1,507 ​ ​ 102 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balances at December 31, 2021 ​ $ 3,699 ​ $ 4,160 ​ $ 309 ​ $ (770) ​
Summary of the significant reclassifications out of accumulated other comprehensive income (loss) by component	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized Net Periodic ​ ​ ​ Benefit Credit (1)(2) ​ 2021 2020 ​ ​ (in thousands) Amortization of net actuarial gain ​ $ 539 ​ $ 589 ​ Amortization of prior service credit ​ ​ — ​ 1 ​ Pension settlement expense (3) ​ ​ — ​ (89) ​ Total, pre-tax ​ ​ 539 ​ 501 ​ Tax expense ​ ​ (139) ​ (129) ​ Total, net of tax ​ $ 400 ​ $ 372 ​ (1) Amounts in parentheses indicate increases in expense or loss. (2) These components of accumulated other comprehensive income (loss) are included in the computation of net periodic benefit cost (see Note J). (3) Pension settlement expense is related to the supplemental benefit plan (see Note J). ​
Summary of dividends declared	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 ​ ​ Per Share Amount Per Share Amount ​ ​ (in thousands, except per share data) First quarter ​ $ 0.08 ​ $ 2,037 ​ $ 0.08 ​ $ 2,033 ​ Second quarter ​ $ 0.08 ​ $ 2,058 ​ $ 0.08 ​ $ 2,049 ​ Third quarter ​ $ 0.08 ​ $ 2,050 ​ $ 0.08 ​ $ 2,040 ​ Fourth quarter ​ $ 0.08 ​ $ 1,994 ​ $ 0.08 ​ $ 2,035 ​

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2021
SHARE-BASED COMPENSATION
Summary of the Company's restricted stock unit award program	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ Grant Date ​ ​ ​ Units ​ Fair Value Outstanding – January 1, 2021 ​ 1,841,150 ​ $ 22.09 ​ Granted ​ 136,295 ​ $ 86.96 ​ Vested ​ (442,690) ​ $ 17.18 ​ Forfeited (1) ​ (52,356) ​ $ 29.59 ​ Outstanding – December 31, 2021 ​ 1,482,399 ​ $ 29.25 ​ (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 2021 136,295 ​ $ 86.96 ​ 2020 579,660 ​ $ 19.22 ​ 2019 386,840 ​ $ 27.75 ​

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2021
EARNINGS PER SHARE
Schedule of computation of basic and diluted earnings (loss) per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands, except share and per share data) Basic ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income ​ $ 213,521 ​ $ 71,100 ​ $ 39,985 ​ Effect of unvested restricted stock awards ​ — ​ — ​ (22) ​ Adjusted net income ​ $ 213,521 ​ $ 71,100 ​ $ 39,963 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares ​ 25,471,939 ​ 25,410,232 ​ 25,535,529 ​ Earnings per common share ​ $ 8.38 ​ $ 2.80 ​ $ 1.56 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income ​ $ 213,521 ​ $ 71,100 ​ $ 39,985 ​ Effect of unvested restricted stock awards ​ — ​ — ​ (21) ​ Adjusted net income ​ $ 213,521 ​ $ 71,100 ​ $ 39,964 ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares ​ 25,471,939 ​ 25,410,232 ​ 25,535,529 ​ Effect of dilutive securities ​ 1,300,187 ​ 1,012,291 ​ 914,526 ​ Adjusted weighted-average shares and assumed conversions ​ 26,772,126 ​ 26,422,523 ​ 26,450,055 ​ Earnings per common share ​ $ 7.98 ​ $ 2.69 ​ $ 1.51 ​

OPERATING SEGMENT DATA (Tables)

OPERATING SEGMENT DATA (Tables)	12 Months Ended
	Dec. 31, 2021
OPERATING SEGMENT DATA
Schedule of reportable operating segment information	The following table reflects reportable operating segment information for the years ended December 31: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands) REVENUES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,573,773 ​ $ 2,092,031 ​ $ 2,144,679 ​ ArcBest (1) ​ 1,300,626 ​ 779,115 ​ 738,392 ​ FleetNet ​ 254,087 ​ 205,049 ​ 211,738 ​ Other and eliminations ​ (148,419) ​ (136,032) ​ (106,499) ​ Total consolidated revenues ​ $ 3,980,067 ​ $ 2,940,163 ​ $ 2,988,310 ​ OPERATING EXPENSES ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Salaries, wages, and benefits ​ $ 1,198,253 ​ $ 1,095,694 ​ $ 1,148,761 ​ Fuel, supplies, and expenses ​ 266,139 ​ 209,095 ​ 257,133 ​ Operating taxes and licenses ​ 49,461 ​ 49,300 ​ 50,209 ​ Insurance ​ 37,800 ​ 33,568 ​ 32,516 ​ Communications and utilities ​ 18,773 ​ 17,916 ​ 18,614 ​ Depreciation and amortization ​ 93,799 ​ 94,326 ​ 89,798 ​ Rents and purchased transportation ​ 364,345 ​ 250,159 ​ 221,479 ​ Shared services ​ ​ 263,532 ​ ​ 217,258 ​ ​ 212,773 ​ Gain on sale of property and equipment (2) ​ (8,676) ​ (3,309) ​ (5,892) ​ Innovative technology costs (3) ​ ​ 27,631 ​ ​ 22,458 ​ ​ 13,739 ​ Other ​ 2,009 ​ 6,701 ​ 3,488 ​ Total Asset-Based ​ 2,313,066 ​ 1,993,166 ​ 2,042,618 ​ ArcBest (1) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Purchased transportation ​ 1,097,332 ​ 649,933 ​ 606,113 ​ Supplies and expenses ​ 10,531 ​ 9,627 ​ 10,789 ​ Depreciation and amortization ​ 11,387 ​ 9,714 ​ 11,344 ​ Shared services ​ ​ 132,137 ​ ​ 90,983 ​ ​ 93,961 ​ Gain on sale of subsidiaries (4) ​ ​ (6,923) ​ ​ — ​ ​ — ​ Other ​ ​ 9,765 ​ 9,203 ​ 9,860 ​ Asset impairment (5) ​ ​ — ​ ​ — ​ ​ 26,514 ​ Total ArcBest ​ 1,254,229 ​ 769,460 ​ 758,581 ​ FleetNet ​ 249,543 ​ 201,682 ​ 206,932 ​ Other and eliminations ​ (117,757) ​ (122,423) ​ (83,591) ​ Total consolidated operating expenses ​ $ 3,699,081 ​ $ 2,841,885 ​ $ 2,924,540 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ OPERATING INCOME ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 260,707 ​ $ 98,865 ​ $ 102,061 ​ ArcBest (1) ​ 46,397 ​ 9,655 ​ (20,189) ​ FleetNet ​ 4,544 ​ 3,367 ​ 4,806 ​ Other and eliminations ​ (30,662) ​ (13,609) ​ (22,908) ​ Total consolidated operating income ​ $ 280,986 ​ $ 98,278 ​ $ 63,770 ​ OTHER INCOME (COSTS) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest and dividend income ​ $ 1,275 ​ $ 3,616 ​ $ 6,453 ​ Interest and other related financing costs ​ (8,904) ​ (11,697) ​ (11,467) ​ Other, net (6) ​ 3,797 ​ 2,299 ​ (7,285) ​ Total other costs ​ (3,832) ​ (5,782) ​ (12,299) ​ INCOME BEFORE INCOME TAXES ​ $ 277,154 ​ $ 92,496 ​ $ 51,471 ​ (1) For 2021, includes the operations of MoLo since the November 1, 2021 acquisition (see Note D). (2) For 2021, includes an $8.6 million gain on the sale of unutilized service center property. (3) Represents costs associated with the freight handling pilot test program at ABF Freight. (4) Gain relates to the sale of the labor services portion of the ArcBest segment’s moving business in the second quarter 2021. (5) The ArcBest segment recognized a noncash impairment charge in 2019 related to a portion of the goodwill, customer relationship intangible assets, and revenue equipment associated with the acquisition of truckload and dedicated businesses within the segment (see Note E). (6) Includes the components of net periodic benefit cost other than service cost, including pension settlement and termination expense (see Note J), and proceeds and changes in cash surrender value of life insurance policies. ​ ​ The following table reflects information about revenues from customers and intersegment revenues: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands) Revenues from customers ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,470,529 ​ $ 1,998,549 ​ $ 2,077,287 ​ ArcBest ​ 1,291,679 ​ 770,560 ​ 731,366 ​ FleetNet ​ 213,882 ​ 166,654 ​ 175,055 ​ Other ​ 3,977 ​ 4,400 ​ 4,602 ​ Total consolidated revenues ​ $ 3,980,067 ​ $ 2,940,163 ​ $ 2,988,310 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Intersegment revenues ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 103,244 ​ $ 93,482 ​ $ 67,392 ​ ArcBest ​ ​ 8,947 ​ ​ 8,555 ​ ​ 7,026 ​ FleetNet ​ ​ 40,205 ​ ​ 38,395 ​ ​ 36,683 ​ Other and eliminations ​ ​ (152,396) ​ ​ (140,432) ​ ​ (111,101) ​ Total intersegment revenues ​ $ — ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total segment revenues ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,573,773 ​ ​ 2,092,031 ​ ​ 2,144,679 ​ ArcBest ​ ​ 1,300,626 ​ ​ 779,115 ​ ​ 738,392 ​ FleetNet ​ ​ 254,087 ​ ​ 205,049 ​ ​ 211,738 ​ Other and eliminations ​ ​ (148,419) ​ ​ (136,032) ​ ​ (106,499) ​ Total consolidated revenues ​ $ 3,980,067 ​ $ 2,940,163 ​ $ 2,988,310 ​ ​ The following table provides capital expenditure and depreciation and amortization information by reportable operating segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ 2021 2020 2019 ​ ​ ​ (in thousands) ​ CAPITAL EXPENDITURES, GROSS ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based (1) ​ $ 96,180 ​ $ 85,135 ​ $ 122,437 ​ ArcBest ​ ​ 9,565 ​ ​ 1,258 ​ ​ 3,909 ​ FleetNet ​ 1,174 ​ 675 ​ 590 ​ Other and eliminations (2)(3) ​ 11,193 ​ 17,983 ​ 33,748 ​ ​ ​ $ 118,112 ​ $ 105,051 ​ $ 160,684 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the year ended December 31 ​ ​ ​ 2021 2020 2019 ​ ​ ​ (in thousands) ​ DEPRECIATION AND AMORTIZATION EXPENSE (2) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 93,799 ​ $ 94,326 ​ $ 89,798 ​ ArcBest (4) ​ ​ 11,387 ​ ​ 9,714 ​ ​ 11,344 ​ FleetNet (5) ​ 1,661 ​ 1,622 ​ 1,341 ​ Other and eliminations (2) ​ 17,374 ​ 12,729 ​ 9,983 ​ ​ ​ $ 124,221 ​ $ 118,391 ​ $ 112,466 ​ (1) Includes assets acquired through notes payable of $59.7 million, $61.8 million, and $67.6 million in 2021, 2020, and 2019, respectively. (2) Other and eliminations includes certain assets held for the benefit of multiple segments, including information systems equipment. 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 $23.2 million in 2019. (4) Includes amortization of intangibles of $5.3 million, $3.7 million, and $4.2 million in 2021, 2020, and 2019, respectively. (5) Includes amortization of intangibles which totaled less than $0.1 million in 2021 and $0.2 million in both 2020 and 2019. ​ 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 $32.8 million and $25.6 million for the year ended December 31, 2021 and 2020, respectively, related to innovative technology initiatives. ​
Schedule of revenues from customers and intersegment revenues	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 2019 ​ ​ (in thousands) Revenues from customers ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,470,529 ​ $ 1,998,549 ​ $ 2,077,287 ​ ArcBest ​ 1,291,679 ​ 770,560 ​ 731,366 ​ FleetNet ​ 213,882 ​ 166,654 ​ 175,055 ​ Other ​ 3,977 ​ 4,400 ​ 4,602 ​ Total consolidated revenues ​ $ 3,980,067 ​ $ 2,940,163 ​ $ 2,988,310 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Intersegment revenues ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 103,244 ​ $ 93,482 ​ $ 67,392 ​ ArcBest ​ ​ 8,947 ​ ​ 8,555 ​ ​ 7,026 ​ FleetNet ​ ​ 40,205 ​ ​ 38,395 ​ ​ 36,683 ​ Other and eliminations ​ ​ (152,396) ​ ​ (140,432) ​ ​ (111,101) ​ Total intersegment revenues ​ $ — ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total segment revenues ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Asset-Based ​ $ 2,573,773 ​ ​ 2,092,031 ​ ​ 2,144,679 ​ ArcBest ​ ​ 1,300,626 ​ ​ 779,115 ​ ​ 738,392 ​ FleetNet ​ ​ 254,087 ​ ​ 205,049 ​ ​ 211,738 ​ Other and eliminations ​ ​ (148,419) ​ ​ (136,032) ​ ​ (106,499) ​ Total consolidated revenues ​ $ 3,980,067 ​ $ 2,940,163 ​ $ 2,988,310 ​

ORGANIZATION AND DESCRIPTION _2

ORGANIZATION AND DESCRIPTION OF THE BUSINESS AND FINANCIAL STATEMENT PRESENTATION - Organization (Details)	12 Months Ended
	Dec. 31, 2021segment
Organization and description of business
Number of reportable operating segments	3
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	62.00%
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	82.00%

ACCOUNTING POLICIES - Concentra

ACCOUNTING POLICIES - Concentration (Details) - Minimum	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues | Customer concentration risk
Concentrations
Percentage for concentration of credit risk disclosure	4.00%	4.00%	4.00%
Accounts receivable | Credit concentration risk
Concentrations
Percentage for concentration of credit risk disclosure	7.00%	7.00%

ACCOUNTING POLICIES - Allowance

ACCOUNTING POLICIES - Allowances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Allowances
Allowance for credit losses on trade accounts receivable	$ 8.8	$ 3.6
Increase in amount of allowance for credit losses, including allowance assumed in business acquisition	8
Amount of allowance for credit losses assumed in acquisition	6.5
Write-offs, net of recoveries	$ 2.8

ACCOUNTING POLICIES - Property

ACCOUNTING POLICIES - Property (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2019	Dec. 31, 2020
Property, Plant and Equipment
Long-lived assets impairment		$ 6.5
ArcBest
Property, Plant and Equipment
Long-lived assets impairment		$ 6.5
Held-for-sale | Other long-term assets
Property, Plant and Equipment
Assets held for sale which are reported within other noncurrent assets	$ 0.6		$ 1.1
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	16 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	15 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 - Business

ACCOUNTING POLICIES - Business combinations (Details) - USD ($) $ in Thousands	Nov. 01, 2021	Dec. 31, 2021
Business Acquisition [Line Items]
Consideration paid, net of cash acquired		$ 239,380
MoLo Solutions, LLC
Business Acquisition [Line Items]
Consideration paid, net of cash acquired	$ 239,398
Contingent consideration		$ 93,700

ACCOUNTING POLICIES - Long Term

ACCOUNTING POLICIES - Long Term Investments (Details) $ in Millions	Dec. 31, 2021USD ($)
ACCOUNTING POLICIES
Carrying value of equity securities without readily determinable fair value	$ 25

ACCOUNTING POLICIES - Book Over

ACCOUNTING POLICIES - Book Overdrafts (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounts Payable
Book Overdrafts
Amount of book overdrafts	$ 22.6	$ 21.3

ACCOUNTING POLICIES - Other Rec

ACCOUNTING POLICIES - Other Recognition and Disclosure (Details)	12 Months Ended
	Dec. 31, 2021
Other Recognition and Disclosure
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	Nov. 02, 2021	Jan. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Equity
Cost of repurchased shares			$ 83,100	$ 6,595	$ 9,110
Accelerated Share Repurchase Agreement ("ASR")
Equity
Amount paid in accelerated repurchase	$ 100,000
Number of shares repurchased during the period	709,287		709,287
Cost of repurchased shares	$ 75,000		$ 75,000
Amount of unsettled forward contract classified within stockholders' equity as additional paid in capital.			$ 25,000
Accelerated Share Repurchase Agreement ("ASR") | Subsequent Event
Equity
Number of shares repurchased during the period		214,763

ACCOUNTING POLICIES - Share-Bas

ACCOUNTING POLICIES - Share-Based Compensation (Details) - Restricted Stock Units	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee
Share-Based Compensation
Vesting period	3 years	4 years	4 years	4 years	5 years
Nonemployee Director
Share-Based Compensation
Vesting period	1 year	1 year	1 year	1 year	1 year	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, 2021	Dec. 31, 2020
Fair value disclosure
Cash and cash equivalents	$ 76,620	$ 303,954
Short-term investments	48,339	65,408
Concentrations of Credit Risk of Financial Instruments
Cash, cash equivalents and short-term investments not FDIC-insured	42,600	156,400
Cash deposits
Fair value disclosure
Cash and cash equivalents	72,790	240,687
Variable rate demand notes
Fair value disclosure
Cash and cash equivalents	230	29,066
Money market funds
Fair value disclosure
Cash and cash equivalents	3,600	34,201
Certificates of deposit
Fair value disclosure
Short-term investments	$ 48,339	53,297
Treasury instruments
Fair value disclosure
Short-term investments		$ 12,111

FINANCIAL INSTRUMENTS AND FAI_4

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Debt (Details) $ in Thousands	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
New England Teamsters and Trucking Industry Pension Fund | Nonunion Defined Benefit Pension Plan | Asset Based
Fair value disclosure
Outstanding withdrawal liability	$ 20,800
New England Teamsters and Trucking Industry Pension Fund | Nonunion Defined Benefit Pension Plan | Asset Based | Accrued expenses
Fair value disclosure
Outstanding withdrawal liability	700
New England Teamsters and Trucking Industry Pension Fund | Nonunion Defined Benefit Pension Plan | Asset Based | Other long-term liabilities
Fair value disclosure
Outstanding withdrawal liability	20,100
Carrying value
Fair value disclosure
Financial instruments	246,299	$ 305,623
Fair value disclosure
Fair value disclosure
Financial instruments	249,458	312,749
Credit Facility | Carrying value | Level 2
Fair value disclosure
Financial instruments	50,000	70,000
Credit Facility | Fair value disclosure | Level 2
Fair value disclosure
Financial instruments	50,000	70,000
Notes payable | Carrying value | Level 2
Fair value disclosure
Financial instruments	175,530	214,216
Notes payable | Fair value disclosure | Level 2
Fair value disclosure
Financial instruments	$ 175,937	$ 217,226
New England Pension Fund withdrawal liability | Discount Rate
Fair value disclosure
Measurement input	0.031	0.026
New England Pension Fund withdrawal liability | Carrying value | Level 2
Fair value disclosure
Financial instruments	$ 20,769	$ 21,407
New England Pension Fund withdrawal liability | Fair value disclosure | Level 2
Fair value disclosure
Financial instruments	$ 23,521	$ 25,523

FINANCIAL INSTRUMENTS AND FAI_5

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Assets and Liabilities (Details) - Recurring basis - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets:
Assets	$ 8,322	$ 37,156
Liabilities:
Liabilities	94,155
Cash and cash equivalents
Assets:
Money market funds	3,600	34,201
Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	3,848	2,955
Interest rate swaps	874
Other long-term liabilities
Liabilities:
Interest rate swap	455	1,622
Contingent consideration	93,700
Level 1
Assets:
Assets	7,448	37,156
Level 1 | Cash and cash equivalents
Assets:
Money market funds	3,600	34,201
Level 1 | Other long-term assets
Assets:
Equity, bond, and money market mutual funds held in trust related to the Voluntary Savings Plan	3,848	2,955
Level 2
Assets:
Assets	874
Liabilities:
Liabilities	455
Level 2 | Other long-term assets
Assets:
Interest rate swaps	874
Level 2 | Other long-term liabilities
Liabilities:
Interest rate swap	455	$ 1,622
Level 3
Liabilities:
Liabilities	93,700
Level 3 | Other long-term liabilities
Liabilities:
Contingent consideration	$ 93,700

FINANCIAL INSTRUMENTS AND FAI_6

FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Nonrecurring (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Valuation Technique, Discounted Cash Flow [Member]
Fair value measurement
Amount of increase in contingent consideration liability of a 100 basis point decrease in discount rate in estimation of fair value	$ 4,200
Discount Rate | Valuation Technique, Discounted Cash Flow [Member]
Fair value measurement
Measurement input	0.090
Level 3 | Nonrecurring basis
Fair value measurement
Assets	$ 0	$ 0

ACQUISITION - MoLo (Details)

ACQUISITION - MoLo (Details) - USD ($) $ in Thousands	Nov. 01, 2021	Dec. 31, 2021
Business Acquisition
Consideration paid, net of cash acquired		$ 239,380
Purchase Consideration
Net cash consideration, including estimated post-closing adjustments		$ 239,380
MoLo Solutions, LLC
Business Acquisition
Consideration paid, net of cash acquired	$ 239,398
Purchase Consideration
Net cash consideration, including estimated post-closing adjustments	239,398
Contingent consideration	93,700
Total purchase consideration	$ 333,098
MoLo Solutions, LLC | 100% of target
Business Acquisition
Adjusted EBITDA target percentage	100.00%
Contingent consideration, target	$ 215,000
MoLo Solutions, LLC | 80% of target
Business Acquisition
Adjusted EBITDA target percentage	80.00%
Contingent consideration, low range	$ 95,000
MoLo Solutions, LLC | 300% of target
Business Acquisition
Adjusted EBITDA target percentage	300.00%
Contingent consideration, high range	$ 455,000

ACQUISITION - Estimated fair va

ACQUISITION - Estimated fair values of acquired assets and liabilities (Details) - USD ($) $ in Thousands	2 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Nov. 01, 2021
Purchase Allocation
Goodwill	$ 300,337	$ 300,337	$ 88,320
Operating revenues		3,980,067	2,940,163	$ 2,988,310
Operating income (loss)		$ 280,986	$ 98,278	$ 63,770
MoLo Solutions, LLC
Purchase Allocation
Accounts receivable, less allowances					$ 136,522
Prepaid expenses					766
Property and equipment, net					2,309
Operating lease right-of use assets					844
Intangible assets					76,900
Other assets					323
Total identifiable assets acquired					217,664
Accounts payable					94,909
Accrued expenses and other current liabilities					2,643
Operating lease liabilities					983
Total liabilities					98,535
Total identifiable net assets					119,129
Goodwill					213,969
Net assets acquired					333,098
Fair value of accounts receivable acquired					136,500
Gross contractual amount					143,000
Uncollectible amount					$ 6,500
Operating revenues	120,300
Operating income (loss)	(1,200)
Acquisition related costs	$ 6,000

ACQUISITION - Proforma Suppleme

ACQUISITION - Proforma Supplemental Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Pro forma supplemental information
Revenues	$ 4,488,564	$ 3,213,722
Income before income taxes	266,866	63,622
Net income	$ 205,728	$ 48,290
Diluted EPS	$ 7.68	$ 1.83

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details) - USD ($) $ in Thousands	Oct. 01, 2020	Dec. 31, 2021	Dec. 31, 2019
Goodwill by reportable operating segment
Balance at the beginning of the period		$ 88,320
Goodwill acquired		213,969
Goodwill divested		(1,952)
Balance at the end of the period		300,337
Accumulated impairment		(20,000)
Goodwill impairment	$ 0
ArcBest
Goodwill by reportable operating segment
Balance at the beginning of the period		87,690
Goodwill acquired		213,969
Goodwill divested		(1,952)
Balance at the end of the period		299,707
Accumulated impairment		(20,000)
Goodwill impairment			$ 20,000
FleetNet
Goodwill by reportable operating segment
Balance at the beginning of the period		630
Balance at the end of the period		$ 630

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Intangible (Details) - USD ($) $ in Thousands	Oct. 01, 2021	Oct. 01, 2020	Dec. 31, 2021	Dec. 31, 2019	Dec. 31, 2020
Finite-lived intangible assets
Weighted Average Amortization Period			11 years
Cost			$ 130,656		$ 53,701
Accumulated Amortization			36,376		31,020
Net Value			94,280		22,681
Total intangible assets
Cost			162,956		86,001
Net Value			126,580		54,981
Impairment Assessment of Intangible Assets
Long-lived assets impairment				$ 6,500
Impairment of indefinite-lived intangible assets	$ 0	$ 0
ArcBest
Impairment Assessment of Intangible Assets
Long-lived assets impairment				6,500
Revenue equipment | ArcBest
Impairment Assessment of Intangible Assets
Impairment of revenue equipment				500
Trade name
Indefinite-lived intangible assets
Net Value			$ 32,300		32,300
Customer relationships
Finite-lived intangible assets
Weighted Average Amortization Period			12 years
Cost			$ 100,321		52,721
Accumulated Amortization			35,072		30,477
Net Value			$ 65,249		22,244
Customer relationships | ArcBest
Impairment Assessment of Intangible Assets
Impairment of finite-lived intangible assets				$ 6,000
Other intangible assets
Finite-lived intangible assets
Weighted Average Amortization Period			8 years
Cost			$ 30,335		980
Accumulated Amortization			1,304		543
Net Value			$ 29,031		$ 437

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS - Amortization (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Future amortization for intangible assets
2022	$ 12,920
2023	12,826
2024	12,793
2025	12,778
2025	8,671
Thereafter	34,292
Net Value	$ 94,280	$ 22,681

INCOME TAXES - Provision (Detai

INCOME TAXES - Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current provision:
Federal	$ 56,451	$ 10,001	$ 2,202
State	14,430	3,267	1,813
Foreign	341	413	2,060
Current tax provision	71,222	13,681	6,075
Deferred provision (benefit):
Federal	(6,098)	5,948	4,196
State	(1,554)	1,789	1,221
Foreign	63	(22)	(6)
Deferred tax provision (benefit)	(7,589)	7,715	5,411
Total provision (benefit) for income taxes	$ 63,633	$ 21,396	$ 11,486

INCOME TAXES - Deferred income

INCOME TAXES - Deferred income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Components of the deferred tax provision or benefit
Amortization, depreciation, and basis differences for property, plant and equipment and other long-lived assets	$ 1,451	$ 4,975	$ 16,255
Amortization of intangibles and impairment	(536)	183	(6,933)
Changes in reserves for workers' compensation, third-party casualty, and cargo claims	(3,294)	(182)	(1,880)
Revenue recognition	(1,445)	(1,481)	(1,437)
Allowance for credit losses	156	(652)	541
Nonunion pension and other retirement plans	(3)	957	564
Multiemployer pension fund withdrawal	164	157	150
Federal and state net operating loss carryforwards utilized (generated)	(300)	(259)	59
State depreciation adjustments	598	343	(1,302)
Share-based compensation	(984)	(195)	(709)
Valuation allowance increase	911	617	383
Other accrued expenses	(4,097)	1,663	(699)
Prepaid expenses	(788)	1,207	1,782
Operating lease right-of-use assets/liabilities - net	(228)	(13)	(1,049)
Other	806	395	(314)
Deferred tax provision (benefit)	$ (7,589)	$ 7,715	$ 5,411

INCOME TAXES - Deferred (Detail

INCOME TAXES - Deferred (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Accrued expenses	$ 47,683	$ 40,502
Operating lease liabilities	30,590	33,933
Supplemental pension liabilities	97	103
Multiemployer pension fund withdrawal	5,247	5,409
Postretirement liabilities other than pensions	4,441	4,871
Share-based compensation	6,755	5,827
Federal and state net operating loss carryforwards	1,652	1,353
Revenue recognition	2,778	1,426
Other	266	1,297
Total deferred tax assets	99,509	94,721
Valuation allowance	(2,196)	(1,284)
Total deferred tax assets, net of valuation allowance	97,313	93,437
Deferred tax liabilities:
Amortization, depreciation, and basis differences for property, plant and equipment, and other long-lived assets	114,999	113,092
Operating lease right-of-use assets	29,403	32,923
Intangibles	6,966	7,520
Prepaid expenses	5,368	6,151
Total deferred tax liabilities	156,736	159,686
Net deferred tax liabilities	$ (59,423)	$ (66,249)

INCOME TAXES - Rate Reconciliat

INCOME TAXES - Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation between the effective income tax rate, as computed on income (loss) before income taxes, and the statutory federal income tax rate
Statutory federal rate (as a percent)	21.00%	21.00%	21.00%
Income tax provision at the statutory federal rate	$ 58,202	$ 19,424	$ 10,809
Federal income tax effects of:
State income taxes	(2,704)	(1,062)	(637)
Nondeductible expenses	3,596	1,395	1,344
Life insurance proceeds and changes in cash surrender value	(866)	(488)	(775)
Alternative fuel tax credit		(1,261)	(2,340)
Net increase in valuation allowances	887	617	382
Net increase (decrease) in uncertain tax positions	854	(933)	(20)
Settlement of share-based compensation	(6,140)	420	388
Nonunion pension termination expense			1,040
Foreign tax credits generated	(404)	(391)	(2,054)
Federal research and development tax credits	(2,044)	(2,078)	(1,354)
Other	(1,028)	306	(385)
Federal income tax provision	50,353	15,949	6,398
State income tax provision	12,876	5,056	3,034
Foreign income tax provision	404	391	2,054
Total provision (benefit) for income taxes	$ 63,633	$ 21,396	$ 11,486
Effective tax (benefit) rate (as a percent)	23.00%	23.10%	22.30%
Income taxes paid, excluding income tax refunds	$ 77,500	$ 28,600	$ 28,100
Income tax refunds	$ 19,400	$ 13,300	$ 13,100

INCOME TAXES - ASC Topic 718 (D

INCOME TAXES - ASC Topic 718 (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Pronouncements
Effective tax (benefit) rate (as a percent)	23.00%	23.10%	22.30%
Maximum
Accounting Pronouncements
Tax benefit realized from dividends on share-based payment awards	$ 0.1	$ 0.1	$ 0.1
ASC Topic 718, Compensation - Stock Compensation
Accounting Pronouncements
Effective tax (benefit) rate (as a percent)	(2.80%)	0.50%	0.90%

INCOME TAXES - NOL (Details)

INCOME TAXES - NOL (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)Y	Dec. 31, 2020USD ($)
State
Operating loss carryforwards
Operating loss carryforwards	$ 19.3
Number of prior years with taxable losses | Y	3
Valuation allowance, NOLs	$ 1.1	$ 0.6
State tax department of Panther
Operating loss carryforwards
Operating loss carryforwards	3.4
State tax department of other subsidiaries
Operating loss carryforwards
Operating loss carryforwards	14.8
Federal
Operating loss carryforwards
Operating loss carryforwards	1
Removal of operating loss valuation allowance	$ 0.1
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) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)Y	Dec. 31, 2020USD ($)
State
Tax credit carryforwards
Number of prior years with taxable losses | Y	3
Foreign
Tax credit carryforwards
Valuation allowance, tax credit carryforwards	$ 0.8	$ 0.4
Three-year taxable losses and nexus issues | State
Tax credit carryforwards
Valuation allowance, tax credit carryforwards		$ 0.2
Interest expense carryforwards | State | Maximum
Tax credit carryforwards
Amount of tax credit carryforward reserved	$ 0.1

INCOME TAXES - Uncertain Tax Po

INCOME TAXES - Uncertain Tax Positions (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
INCOME TAXES
Reserve for uncertain tax positions	$ 0.9	$ 0

LEASES - Lease terms (Details)

LEASES - Lease terms (Details)	12 Months Ended
	Dec. 31, 2021
Operating leases
Lessor, Operating Lease, Existence of Option to Terminate [true false]	false
Maximum
Operating leases
Remaining lease term	11 years 1 month 6 days
Operating lease, renewal term	5 years

LEASES - Components of Lease Ex

LEASES - Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
LEASES
Operating lease expense	$ 26,552	$ 24,559	$ 22,291
Variable lease expense	4,128	3,152	3,366
Sublease income	(626)	(398)	(324)
Total operating lease expense	$ 30,054	$ 27,313	$ 25,333

LEASES - Cash flows (Details)

LEASES - Cash flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating leases
Noncash change in operating right-of-use assets	$ 24,023	$ 21,184	$ 20,439
Change in operating lease liabilities	(23,400)	(20,428)	(19,711)
Operating right-of-use assets and lease liabilities, net	623	756	728
Cash paid for amounts included in the measurement of operating lease liabilities	$ (25,909)	$ (23,810)	$ (21,714)

LEASES - Supplemental Balance S

LEASES - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Operating leases
Operating right-of-use assets (long-term)	$ 106,686	$ 115,195
Operating lease liabilities (current)	22,740	21,482
Operating lease liabilities (long-term)	88,835	97,839
Total operating lease liabilities	$ 111,575	$ 119,321
Weighted average remaining lease term (in years)	6 years 10 months 24 days	6 years 8 months 12 days
Weighted average discount rate	2.88%	3.18%
Land and Structures
Operating leases
Operating right-of-use assets (long-term)	$ 106,394	$ 114,908
Operating lease liabilities (current)	22,477	21,207
Operating lease liabilities (long-term)	88,810	97,828
Total operating lease liabilities	111,287	119,035
Equipment and Others
Operating leases
Operating right-of-use assets (long-term)	292	287
Operating lease liabilities (current)	263	275
Operating lease liabilities (long-term)	25	11
Total operating lease liabilities	$ 288	$ 286

LEASES - Maturities of Operatin

LEASES - Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Maturities of operating lease liabilities
2022	$ 25,567
2023	19,800
2024	17,414
2025	14,839
2026	11,404
Thereafter	33,750
Total lease payments	122,774
Less imputed interest	(11,199)
Total operating lease liabilities	111,575	$ 119,321
Future minimum payments for leases that have not yet commenced	$ 85,300
Minimum
Maturities of operating lease liabilities
Lease term for lease commitments that have not yet commenced	10 years
Maximum
Maturities of operating lease liabilities
Lease term for lease commitments that have not yet commenced	12 years
Land and Structures
Maturities of operating lease liabilities
2022	$ 25,302
2023	19,775
2024	17,414
2025	14,839
2026	11,404
Thereafter	33,750
Total lease payments	122,484
Less imputed interest	(11,197)
Total operating lease liabilities	111,287	119,035
Equipment and Others
Maturities of operating lease liabilities
2022	265
2023	25
Total lease payments	290
Less imputed interest	(2)
Total operating lease liabilities	$ 288	$ 286

LONG-TERM DEBT AND FINANCING _3

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Long-term debt obligations
Long-term debt	$ 225,532	$ 284,224
Less current portion	50,615	67,105
Long-term debt, less current portion	$ 174,917	217,119
Weighted-average interest rate (as a percent)	2.60%
Payments under long-term debt obligations
2022	$ 55,060
2023	51,599
2024	95,675
2025	22,856
2026	10,898
Thereafter	293
Total payments	236,381
Less amounts representing interest	10,849
Long-term debt	225,532	284,224
Credit Facility
Long-term debt obligations
Long-term debt	$ 50,000	70,000
Interest rate (as a percent)	1.20%
Payments under long-term debt obligations
2022	$ 807
2023	1,213
2024	51,028
Total payments	53,048
Less amounts representing interest	3,048
Long-term debt	50,000	70,000
Credit Facility | Interest rate swap agreement, maturing on June 30, 2022
Long-term debt obligations
Amount of borrowings covered by the interest rate swap	$ 50,000
Effective fixed interest rate on hedged borrowings (as a percent)	3.12%
Notes payable
Long-term debt obligations
Long-term debt	$ 175,530	214,216
Weighted-average interest rate (as a percent)	2.40%
Payments under long-term debt obligations
2022	$ 54,251
2023	50,386
2024	44,647
2025	22,856
2026	10,898
Thereafter	293
Total payments	183,331
Less amounts representing interest	7,801
Long-term debt	175,530	214,216
Finance lease obligations
Long-term debt obligations
Long-term debt	$ 2	8
Weighted-average interest rate (as a percent)	3.30%
Payments under long-term debt obligations
2022	$ 2
Total payments	2
Long-term debt	$ 2	$ 8

LONG-TERM DEBT AND FINANCING _4

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Assets securing notes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Arrangements
Total assets securing notes payable or held under finance leases	$ 271,665	$ 353,093
Less accumulated depreciation and amortization	88,696	115,424
Net assets securing notes payable or held under finance leases	182,969	237,669
Interest paid, net of capitalized interest	8,700	11,300	$ 10,900
Capitalized interest	500	300	$ 200
Revenue equipment
Financing Arrangements
Total assets securing notes payable or held under finance leases	241,892	326,823
Service, office, and other equipment
Financing Arrangements
Total assets securing notes payable or held under finance leases	$ 29,773	$ 26,270

LONG-TERM DEBT AND FINANCING _5

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Credit Facility (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Feb. 25, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Arrangements
Borrowings under credit facilities		$ 50,000	$ 180,000
Repayment of debt		171,915	326,098	$ 58,938
Outstanding letters of credit		10,600	$ 12,300
Credit Facility
Financing Arrangements
Maximum borrowing capacity		250,000
Additional borrowing capacity that may be requested		125,000
Borrowings under credit facilities		50,000
Repayment of debt		70,000
Remaining borrowing capacity		200,000
Credit Facility | Subsequent Event
Financing Arrangements
Borrowings under credit facilities	$ 65,000
Swing Line Facility
Financing Arrangements
Maximum borrowing capacity		25,000
Swing Line Facility | Subsequent Event
Financing Arrangements
Borrowings under credit facilities	$ 10,000
Letters of Credit, Sub-Facility
Financing Arrangements
Maximum borrowing capacity		$ 20,000

LONG-TERM DEBT AND FINANCING _6

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Interest rate swaps (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021	Dec. 31, 2020	Jan. 02, 2020
Interest rate swap agreement, maturing on June 30, 2022
Financing Arrangements
Notional amount				$ 50
Fixed interest rate payments (as a percent)				1.99%
Interest rate swap agreement, maturing on June 30, 2022 | Other long-term liabilities
Financing Arrangements
Fair value of interest rate swap, liability		$ 0.5	$ 1.4
Interest rate swap agreement, maturing on June 30, 2022 | Credit Facility
Financing Arrangements
Amount of borrowings covered by the interest rate swap		$ 50
Effective fixed interest rate on hedged borrowings (as a percent)		3.12%
Amended interest rate swap agreement, maturing on October 1, 2024
Financing Arrangements
Notional amount		$ 50
Fixed interest rate payments (as a percent)		0.43%
Amended interest rate swap agreement, maturing on October 1, 2024 | Other long-term liabilities
Financing Arrangements
Fair value of interest rate swap, liability			$ 0.2
Amended interest rate swap agreement, maturing on October 1, 2024 | Other long-term assets
Financing Arrangements
Fair value of interest rate swap, asset		$ 0.9
Amended interest rate swap agreement, maturing on October 1, 2024 | Credit Facility | Forecast
Financing Arrangements
Amount of borrowings covered by the interest rate swap	$ 50
Effective fixed interest rate on hedged borrowings (as a percent)	1.56%

LONG-TERM DEBT AND FINANCING _7

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Securitization program (Details) - USD ($) $ in Millions	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Financing Arrangements
Outstanding letters of credit	$ 10.6			$ 12.3
Accounts receivable securitization program
Financing Arrangements
Maximum borrowing capacity		$ 50	$ 125
Additional borrowing capacity that may be requested		$ 100	$ 25
Outstanding letters of credit	10			$ 11.7
Remaining borrowing capacity	$ 40

LONG-TERM DEBT AND FINANCING _8

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Letters of credit & Surety bonds (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Financing Arrangements
Outstanding letters of credit	$ 10.6	$ 12.3
Accounts receivable securitization program
Financing Arrangements
Outstanding letters of credit	10	11.7
Surety bonds
Financing Arrangements
Outstanding surety bonds under uncollateralized bond programs	$ 50.9	$ 61.7

LONG-TERM DEBT AND FINANCING _9

LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Notes Payable (Details) - Notes payable - USD ($) $ in Millions	Feb. 25, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenue equipment | Subsequent Event
Financing Arrangements
Assets financed during the period under promissory note arrangements	$ 6.2
Revenue equipment and software
Financing Arrangements
Assets financed during the period under promissory note arrangements		$ 59.7	$ 61.8

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
ACCRUED EXPENSES.
Workers' compensation, third-party casualty, and loss and damage claims reserves	$ 116,535	$ 103,898
Accrued vacation pay	52,746	51,728
Accrued compensation, including retirement benefits	110,755	67,690
Taxes other than income	10,225	10,468
Other	15,590	12,962
Total accrued expenses	$ 305,851	$ 246,746

EMPLOYEE BENEFIT PLANS - Plan s

EMPLOYEE BENEFIT PLANS - Plan summary (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2019
Nonunion Defined Benefit Pension Plan
Postretirement benefit plans
Noncash charge to pension settlement expense		$ 4
Noncash charge to pension settlement expense, tax benefit		$ 0
Postretirement Health Benefit Plan
Postretirement benefit plans
Unrecognized prior service credit, amortization period	9 years

EMPLOYEE BENEFIT PLANS - Funded

EMPLOYEE BENEFIT PLANS - Funded status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Nonunion Defined Benefit Pension Plan
Change in benefit obligations
Interest cost			$ 624
Supplemental Benefit Plan
Change in benefit obligations
Benefit obligations at beginning of period	$ 392	$ 3,236
Interest cost	4	9	39
Actuarial (gain) loss	(15)	34
Benefits paid		(2,887)
Benefit obligations at end of period	381	392	3,236
Change in plan assets
Employer contributions		2,887
Benefits paid		(2,887)
Funded status at period end	(381)	(392)
Accumulated benefit obligation	381	392
Postretirement Health Benefit Plan
Change in benefit obligations
Benefit obligations at beginning of period	18,751	20,630
Service cost	192	187	320
Interest cost	427	576	1,212
Actuarial (gain) loss	(1,736)	(2,027)
Benefits paid	(642)	(615)
Benefit obligations at end of period	16,992	18,751	$ 20,630
Change in plan assets
Employer contributions	642	615
Benefits paid	(642)	(615)
Funded status at period end	(16,992)	(18,751)
Accumulated benefit obligation	$ 16,992	$ 18,751

EMPLOYEE BENEFIT PLANS - Recogn

EMPLOYEE BENEFIT PLANS - Recognized in Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Amounts recognized in the consolidated balance sheets
Pension and postretirement liabilities, less current portion	$ (16,733)	$ (18,555)
Supplemental Benefit Plan
Amounts recognized in the consolidated balance sheets
Pension and postretirement liabilities, less current portion	(381)	(392)
Liabilities recognized	(381)	(392)
Postretirement Health Benefit Plan
Amounts recognized in the consolidated balance sheets
Current portion of pension and postretirement liabilities	(640)	(588)
Pension and postretirement liabilities, less current portion	(16,352)	(18,163)
Liabilities recognized	$ (16,992)	$ (18,751)

EMPLOYEE BENEFIT PLANS - Compon

EMPLOYEE BENEFIT PLANS - Components of cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Components of net periodic benefit cost
Pension settlement expense		$ 89	$ 8,505
Nonunion Defined Benefit Pension Plan
Components of net periodic benefit cost
Interest cost			624
Expected return on plan assets			(31)
Pension settlement expense			4,164
Amortization of net actuarial (gain) loss			260
Net periodic benefit cost			5,017
Noncash charge to pension settlement expense			4,000
Supplemental Benefit Plan
Components of net periodic benefit cost
Interest cost	$ 4	9	39
Pension settlement expense		89	370
Amortization of net actuarial (gain) loss	9	8	95
Net periodic benefit cost	13	106	504
Postretirement Health Benefit Plan
Components of net periodic benefit cost
Service cost	192	187	320
Interest cost	427	576	1,212
Amortization of prior service credit		(1)	(33)
Amortization of net actuarial (gain) loss	(548)	(597)	898
Net periodic benefit cost	$ 71	$ 165	$ 2,397

EMPLOYEE BENEFIT PLANS - Settle

EMPLOYEE BENEFIT PLANS - Settlement distributions and expense (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Distributions and pension settlement expense
Pension settlement expense, pre-tax	$ 89	$ 8,505
Nonunion Defined Benefit Pension Plan
Distributions and pension settlement expense
Pension settlement distributions		33,938
Pension settlement expense, pre-tax		$ 4,164
Pension settlement expense per diluted share, net of taxes		$ 0.12
Lump-sum distributions		$ 18,400
Nonparticipating annuity contract purchase price		14,000
Transfer of remaining obligation to PGBC		1,500
Noncash charge to pension settlement expense		4,000
Supplemental Benefit Plan
Distributions and pension settlement expense
Pension settlement distributions	2,887	937
Pension settlement expense, pre-tax	$ 89	$ 370
Pension settlement expense per diluted share, net of taxes		$ 0.01
Period of delay for pension settlement distribution to key employees	6 months	6 months

EMPLOYEE BENEFIT PLANS - Includ

EMPLOYEE BENEFIT PLANS - Included in AOCI (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
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) loss	$ 40	$ 64
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) loss	$ (5,642)	$ (4,454)

EMPLOYEE BENEFIT PLANS - Discou

EMPLOYEE BENEFIT PLANS - Discount rate and assumptions (Details)	3 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Nonunion Defined Benefit Pension Plan
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	3.70%	3.80%			3.90%
Expected return on plan assets, net of estimated expenses (as a percent)	0.00%	0.00%			1.40%
Supplemental Benefit Plan
Weighted-average assumptions used to determine nonunion benefit obligations
Discount rate (as a percent)			1.80%	1.10%
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)			1.10%	2.40%	3.60%
Postretirement Health Benefit Plan
Weighted-average assumptions used to determine nonunion benefit obligations
Discount rate (as a percent)			2.70%	2.30%
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)			2.30%	3.10%	4.20%

EMPLOYEE BENEFIT PLANS - Health

EMPLOYEE BENEFIT PLANS - Health care trend rates (Details) - Postretirement Health Benefit Plan	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Assumed health care cost trend rates
Health care cost trend rate assumed for next year (as a percent)	7.00%	7.00%
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	2033	2032

EMPLOYEE BENEFIT PLANS - Future

EMPLOYEE BENEFIT PLANS - Future benefit payments (Details) $ in Thousands	Dec. 31, 2021USD ($)
Supplemental Benefit Plan
Estimated future benefit payments
2027-2031	$ 424
Postretirement Health Benefit Plan
Estimated future benefit payments
2022	640
2023	633
2024	584
2025	605
2026	642
2027-2031	$ 3,522

EMPLOYEE BENEFIT PLANS - Deferr

EMPLOYEE BENEFIT PLANS - Deferred Comp Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Deferred salary agreements
Deferred Compensation Plans
Recorded liabilities	$ 1.5	$ 1.8
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	$ 3.8	3
Voluntary Savings Plan - mutual funds held in trust | Other long-term liabilities
Deferred Compensation Plans
VSP liabilities	$ 3.8	$ 3

EMPLOYEE BENEFIT PLANS - Define

EMPLOYEE BENEFIT PLANS - Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
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	$ 28.3	$ 14.2	$ 13.7
Other Plans
Cash surrender value of life insurance policies	57.2	55.7
Recognized gains associated with changes in the cash surrender value and proceeds from life insurance policies	$ 4.1	2.3	3.7
401(k) Plan
Defined Contribution Plans
Maximum percentage of salary permitted to be deferred by plan participants	69.00%
Rate of employer match on participant contributions	50.00%
Maximum percentage of participants compensation that is eligible for 50% matching contribution	6.00%
Expense for employer contribution to defined contribution plan	$ 7.7	4.6	6.8
Defined Contribution Plan
Defined Contribution Plans
Period of service for participants' full vesting in the employer's contributions	3 years
Expense for employer contribution to defined contribution plan	$ 16.8	$ 12.6	$ 10.9

EMPLOYEE BENEFIT PLANS - Multie

EMPLOYEE BENEFIT PLANS - Multiemployer Plans (Details) - Asset Based $ in Thousands	Aug. 01, 2021	Aug. 01, 2020	Jan. 31, 2020	Aug. 01, 2019	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2021USD ($)plan	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Jan. 01, 2020	Jan. 01, 2019
Multiemployer Plans
Minimum funded percentage of plans in green zone							80.00%
Nonunion Defined Benefit Pension Plan
Multiemployer Plans
Number of multiemployer plans to which ABF Freight currently contributes | plan							25
Maximum funded percentage of plans in yellow zone							80.00%
Maximum funded percentage of plans in red zone							65.00%
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							80.00%
Percentage of contributions to the multiemployer pension plans that are in critical and declining status							56.00%
Percentage of contributions to the multiemployer pension plans that are in critical status							4.00%
Percentage of contributions to the multiemployer pension plans that are in endangered status							4.00%
Total multiemployer pension contributions paid							$ 146,893	$ 142,194	$ 153,746
Nonunion Defined Benefit Pension Plan | Central States Pension Plan
Multiemployer Plans
Multiemployer pension contributions paid, individually significant							$ 71,045	$ 68,704	$ 75,803
Threshold percentage of the entity's contributions relative to total fund contributions, which was exceeded during the period								5.00%	5.00%
Maximum projected time to insolvency without legislative action							4 years
Percentage of contributions to multiemployer pension plan							50.00%	50.00%	50.00%
Actuarially certified projected funded percentage of multiemployer pension plan										19.50%	24.80%
Nonunion Defined Benefit Pension Plan | Western Conference Of Teamsters Pension Plan
Multiemployer Plans
Multiemployer pension contributions paid, individually significant							$ 25,861	$ 23,633	$ 24,860
Nonunion Defined Benefit Pension Plan | Central Pennsylvania Teamsters Pension Plan
Multiemployer Plans
Multiemployer pension contributions paid, individually significant							13,931	$ 13,485	$ 13,907
Threshold percentage of the entity's contributions relative to total fund contributions, which was exceeded during the period								5.00%	5.00%
Nonunion Defined Benefit Pension Plan | Local 710 Pension Fund
Multiemployer Plans
Multiemployer pension contributions paid, individually significant							9,553	$ 9,885	$ 10,164
Threshold percentage of the entity's contributions relative to total fund contributions, which was exceeded during the period			5.00%
Nonunion Defined Benefit Pension Plan | New England Teamsters and Trucking Industry Pension Fund
Multiemployer Plans
Multiemployer pension contributions paid, individually significant							4,357	4,464	4,802
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)					23 years
Nonunion Defined Benefit Pension Plan | Other Pension Plans
Multiemployer Plans
Multiemployer pension contributions paid, individually insignificant							$ 22,146	22,023	24,210
Nonunion Defined Benefit Pension Plan | Western Pennsylvania Teamsters And Employers Pension Fund
Multiemployer Plans
Percentage of contributions to individually insignificant multiemployer pension plan							1.00%
Nonunion Defined Benefit Pension Plan | New York State Teamsters Conference Pension and Retirement Fund
Multiemployer Plans
Percentage of contributions to individually insignificant multiemployer pension plan							1.00%
Nonunion Defined Benefit Pension Plan | North Jersey Welfare Fund
Multiemployer Plans
Percentage of contributions to individually insignificant multiemployer pension plan							2.00%
Multiemployer health and welfare plans
Multiemployer Plans
Number of multiemployer plans to which ABF Freight currently contributes | plan							38
Total multiemployer pension contributions paid							$ 176,200	$ 163,800	$ 172,000
Percentage increase in contribution rate for time worked related to benefit costs	4.30%	4.00%		3.90%
Unionized employees concentration risk | Number of employees
Multiemployer Plans
Percentage of Asset-Based segment employees covered under collective bargaining agreement with the IBT							82.00%

STOCKHOLDERS' EQUITY - AOCI (De

STOCKHOLDERS' EQUITY - AOCI (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income
Total after-tax amount	$ 929,067	$ 828,593	$ 763,043	$ 717,682
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income
Total pre-tax amount	4,977	1,586	260
Total after-tax amount	3,699	1,190	203	$ (14,238)
Unrecognized Net Periodic Benefit Credit
Accumulated Other Comprehensive Income
Total pre-tax amount	5,602	4,390	2,898
Total after-tax amount	4,160	3,260	2,152
Interest Rate Swap
Accumulated Other Comprehensive Income
Total pre-tax amount	419	(1,622)	(563)
Total after-tax amount	309	(1,198)	(416)
Foreign Currency Translation
Accumulated Other Comprehensive Income
Total pre-tax amount	(1,044)	(1,182)	(2,075)
Total after-tax amount	$ (770)	$ (872)	$ (1,533)

STOCKHOLDERS' EQUITY - AOCI com

STOCKHOLDERS' EQUITY - AOCI components (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Changes in accumulated other comprehensive income (loss), net of tax, by component
Balances	$ 828,593	$ 763,043	$ 717,682
OTHER COMPREHENSIVE INCOME, net of tax	2,509	987	14,441
Balances	929,067	828,593	763,043
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss), net of tax, by component
Balances	1,190	203	(14,238)
Other comprehensive income (loss) before reclassifications	2,909	1,359
Amounts reclassified from accumulated other comprehensive income (loss)	(400)	(372)
OTHER COMPREHENSIVE INCOME, net of tax	2,509	987	14,441
Balances	3,699	1,190	203
Unrecognized Net Periodic Benefit Credit
Changes in accumulated other comprehensive income (loss), net of tax, by component
Balances	3,260	2,152
Other comprehensive income (loss) before reclassifications	1,300	1,480
Amounts reclassified from accumulated other comprehensive income (loss)	(400)	(372)
OTHER COMPREHENSIVE INCOME, net of tax	900	1,108
Balances	4,160	3,260	2,152
Interest Rate Swap
Changes in accumulated other comprehensive income (loss), net of tax, by component
Balances	(1,198)	(416)
Other comprehensive income (loss) before reclassifications	1,507	(782)
OTHER COMPREHENSIVE INCOME, net of tax	1,507	(782)
Balances	309	(1,198)	(416)
Foreign Currency Translation
Changes in accumulated other comprehensive income (loss), net of tax, by component
Balances	(872)	(1,533)
Other comprehensive income (loss) before reclassifications	102	661
OTHER COMPREHENSIVE INCOME, net of tax	102	661
Balances	$ (770)	$ (872)	$ (1,533)

STOCKHOLDERS' EQUITY - Reclass

STOCKHOLDERS' EQUITY - Reclass (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Unrecognized Net Periodic Benefit Credit
Significant reclassifications out of accumulated other comprehensive loss by component
Total, pre-tax	$ 539	$ 501
Tax expense	(139)	(129)
Total, net of tax	400	372
Amortization of net actuarial gain
Significant reclassifications out of accumulated other comprehensive loss by component
Total, pre-tax	$ 539	589
Amortization of prior service credit
Significant reclassifications out of accumulated other comprehensive loss by component
Total, pre-tax		1
Pension settlement expense
Significant reclassifications out of accumulated other comprehensive loss by component
Total, pre-tax		$ (89)

STOCKHOLDERS' EQUITY - Dividend

STOCKHOLDERS' EQUITY - Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands	Jan. 28, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Dividends on Common Stock
Dividends declared (in dollars per share)		$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.32	$ 0.32	$ 0.32
Dividend Amount		$ 1,994	$ 2,050	$ 2,058	$ 2,037	$ 2,035	$ 2,040	$ 2,049	$ 2,033	$ 8,139	$ 8,157	$ 8,187
Subsequent Event
Dividends on Common Stock
Dividends declared (in dollars per share)	$ 0.08

STOCKHOLDERS' EQUITY - Treasury

STOCKHOLDERS' EQUITY - Treasury Stock (Details) - USD ($) $ in Thousands	Nov. 02, 2021	Jan. 31, 2022	Feb. 25, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 28, 2021
Treasury Stock
Cost of repurchased shares				$ 83,100	$ 6,595	$ 9,110
Forward contract for accelerated share repurchase				$ (25,000)
Treasury stock, at cost, shares				4,492,514	3,656,938
Existing Share Repurchase Program and ASR
Treasury Stock
Number of shares repurchased during the period				835,576
Cost of repurchased shares				$ 83,100
Existing Share Repurchase Program
Treasury Stock
Amount of stock repurchases authorized							$ 50,000
Amount available for repurchase				$ 66,900
Existing Share Repurchase Program | Subsequent Event
Treasury Stock
Number of shares repurchased during the period			79,676
Cost of repurchased shares			$ 6,900
Amount available for repurchase		$ 41,900
Accelerated Share Repurchase Agreement ("ASR")
Treasury Stock
Amount paid in accelerated repurchase	$ 100,000
Number of shares repurchased during the period	709,287			709,287
Cost of repurchased shares	$ 75,000			$ 75,000
Amount of unsettled forward contract classified within stockholders' equity as additional paid in capital.				$ 25,000
Accelerated Share Repurchase Agreement ("ASR") | Subsequent Event
Treasury Stock
Number of shares repurchased during the period		214,763
Forward contract for accelerated share repurchase		$ 25,000

SHARE-BASED COMPENSATION (Detai

SHARE-BASED COMPENSATION (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based compensation
Number of shares authorized	4,900,000
Restricted Stock Units
Award activity
Outstanding at the beginning of the period (in shares)	1,841,150
Granted (in shares)	136,295	579,660	386,840
Vested (in shares)	(442,690)
Forfeited (in shares)	(52,356)
Outstanding at the end of the period (in shares)	1,482,399	1,841,150
Weighted-Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 22.09
Granted (in dollars per share)	86.96	$ 19.22	$ 27.75
Vested (in dollars per share)	17.18
Forfeited (in dollars per share)	29.59
Outstanding at the end of the period (in dollars per share)	$ 29.25	$ 22.09
Other disclosure
Fair value of restricted stock awards vested	$ 36.4	$ 7.8	$ 4.9
Unrecognized compensation cost	$ 16.9
Weighted-average period of recognition of unrecognized compensation cost	1 year 4 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, 2021	Dec. 31, 2020	Dec. 31, 2019
Basic, numerator:
Net income	$ 213,521	$ 71,100	$ 39,985
Effect of unvested restricted stock awards			(22)
Adjusted net income	$ 213,521	$ 71,100	$ 39,963
Basic, denominator:
Weighted-average shares	25,471,939	25,410,232	25,535,529
Earnings per common share (in dollars per share)	$ 8.38	$ 2.80	$ 1.56
Diluted, numerator:
Net income	$ 213,521	$ 71,100	$ 39,985
Effect of unvested restricted stock awards			(21)
Adjusted net income	$ 213,521	$ 71,100	$ 39,964
Diluted, denominator:
Weighted-average shares	25,471,939	25,410,232	25,535,529
Effect of dilutive securities	1,300,187	1,012,291	914,526
Adjusted weighted-average shares and assumed conversions	26,772,126	26,422,523	26,450,055
Earnings per common share (in dollars per share)	$ 7.98	$ 2.69	$ 1.51

EARNINGS PER SHARE - Antidiluti

EARNINGS PER SHARE - Antidilutive securities (Details) shares in Millions	12 Months Ended
	Dec. 31, 2019shares
Stock awards
Antidilutive securities
Antidilutive securities	0.2

OPERATING SEGMENT DATA - Revenu

OPERATING SEGMENT DATA - Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues
Revenues	$ 3,980,067	$ 2,940,163	$ 2,988,310
Asset Based
Revenues
Revenues	2,470,529	1,998,549	2,077,287
ArcBest
Revenues
Revenues	1,291,679	770,560	731,366
FleetNet
Revenues
Revenues	213,882	166,654	175,055
Operating Segments | Asset Based
Revenues
Revenues	2,573,773	2,092,031	2,144,679
Operating Segments | ArcBest
Revenues
Revenues	1,300,626	779,115	738,392
Operating Segments | FleetNet
Revenues
Revenues	254,087	205,049	211,738
Other and eliminations
Revenues
Revenues	$ (148,419)	$ (136,032)	$ (106,499)

OPERATING SEGMENT DATA - Operat

OPERATING SEGMENT DATA - Operating expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING EXPENSES
Salaries, wages, and benefits	$ 1,550,859	$ 1,368,588	$ 1,408,409
Fuel, supplies, and expenses	324,380	250,221	316,047
Depreciation and amortization	124,221	118,391	112,466
Gain on sale of subsidiaries	(6,923)
Gain on sale of property and equipment	(8,520)	(2,376)	(5,247)
Other	129,571	129,850	126,146
Asset impairment			26,514
Total consolidated operating expenses	3,699,081	2,841,885	2,924,540
Operating Segments | Asset Based
OPERATING EXPENSES
Salaries, wages, and benefits	1,198,253	1,095,694	1,148,761
Fuel, supplies, and expenses	266,139	209,095	257,133
Operating taxes and licenses	49,461	49,300	50,209
Insurance	37,800	33,568	32,516
Communications and utilities	18,773	17,916	18,614
Depreciation and amortization	93,799	94,326	89,798
Rents and purchased transportation	364,345	250,159	221,479
Shared services	263,532	217,258	212,773
Gain on sale of property and equipment	(8,676)	(3,309)	(5,892)
Innovative technology costs	27,631	22,458	13,739
Other	2,009	6,701	3,488
Total consolidated operating expenses	2,313,066	1,993,166	2,042,618
Operating Segments | Asset Based | Land and structures
OPERATING EXPENSES
Gain on sale of property and equipment	(8,600)
Operating Segments | ArcBest
OPERATING EXPENSES
Purchased transportation	1,097,332	649,933	606,113
Supplies and expenses	10,531	9,627	10,789
Depreciation and amortization	11,387	9,714	11,344
Shared services	132,137	90,983	93,961
Gain on sale of subsidiaries	(6,923)
Other	9,765	9,203	9,860
Asset impairment			26,514
Total consolidated operating expenses	1,254,229	769,460	758,581
Operating Segments | ArcBest | Land and structures
OPERATING EXPENSES
Gain on sale of subsidiaries	(6,900)
Operating Segments | FleetNet
OPERATING EXPENSES
Depreciation and amortization	1,661	1,622	1,341
Total consolidated operating expenses	249,543	201,682	206,932
Other and eliminations
OPERATING EXPENSES
Depreciation and amortization	17,374	12,729	9,983
Total consolidated operating expenses	$ (117,757)	$ (122,423)	$ (83,591)

OPERATING SEGMENT DATA - Income

OPERATING SEGMENT DATA - Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING INCOME
Operating income	$ 280,986	$ 98,278	$ 63,770
OTHER INCOME (COSTS)
Interest and dividend income	1,275	3,616	6,453
Interest and other related financing costs	(8,904)	(11,697)	(11,467)
Other, net	3,797	2,299	(7,285)
Total other costs	(3,832)	(5,782)	(12,299)
INCOME BEFORE INCOME TAXES	277,154	92,496	51,471
Operating Segments | Asset Based
OPERATING INCOME
Operating income	260,707	98,865	102,061
Operating Segments | ArcBest
OPERATING INCOME
Operating income	46,397	9,655	(20,189)
Operating Segments | FleetNet
OPERATING INCOME
Operating income	4,544	3,367	4,806
Other and eliminations
OPERATING INCOME
Operating income	$ (30,662)	$ (13,609)	$ (22,908)

OPERATING SEGMENT DATA - Reve_2

OPERATING SEGMENT DATA - Revenue from customers (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues
Revenues	$ 3,980,067	$ 2,940,163	$ 2,988,310
Asset Based
Revenues
Revenues	2,470,529	1,998,549	2,077,287
ArcBest
Revenues
Revenues	1,291,679	770,560	731,366
FleetNet
Revenues
Revenues	213,882	166,654	175,055
Corporate and Other
Revenues
Revenues	3,977	4,400	4,602
Operating Segments | Asset Based
Revenues
Revenues	2,573,773	2,092,031	2,144,679
Operating Segments | ArcBest
Revenues
Revenues	1,300,626	779,115	738,392
Operating Segments | FleetNet
Revenues
Revenues	254,087	205,049	211,738
Intersegment revenues
Revenues
Revenues	(152,396)	(140,432)	(111,101)
Intersegment revenues | Asset Based
Revenues
Revenues	103,244	93,482	67,392
Intersegment revenues | ArcBest
Revenues
Revenues	8,947	8,555	7,026
Intersegment revenues | FleetNet
Revenues
Revenues	40,205	38,395	36,683
Other and eliminations
Revenues
Revenues	$ (148,419)	$ (136,032)	$ (106,499)

OPERATING SEGMENT DATA - Capita

OPERATING SEGMENT DATA - Capital expenditures, depreciation and amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	$ 118,112	$ 105,051	$ 160,684
DEPRECIATION AND AMORTIZATION EXPENSE	124,221	118,391	112,466
Amortization of intangibles	5,357	4,012	4,367
Research and development costs	32,800	25,600
Operating Segments | Asset Based
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	96,180	85,135	122,437
DEPRECIATION AND AMORTIZATION EXPENSE	93,799	94,326	89,798
Assets acquired through notes payable	59,700	61,800	67,600
Operating Segments | ArcBest
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	9,565	1,258	3,909
DEPRECIATION AND AMORTIZATION EXPENSE	11,387	9,714	11,344
Amortization of intangibles	5,300	3,700	4,200
Operating Segments | FleetNet
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	1,174	675	590
DEPRECIATION AND AMORTIZATION EXPENSE	1,661	1,622	1,341
Amortization of intangibles		200	200
Operating Segments | Maximum | FleetNet
OPERATING SEGMENT DATA
Amortization of intangibles	100
Other and eliminations
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	11,193	17,983	33,748
DEPRECIATION AND AMORTIZATION EXPENSE	$ 17,374	$ 12,729	9,983
Assets acquired through notes payable			$ 23,200

OPERATING SEGMENT DATA - Oper_2

OPERATING SEGMENT DATA - Operating Expenses by Category (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING EXPENSES
Salaries, wages, and benefits	$ 1,550,859	$ 1,368,588	$ 1,408,409
Rents, purchased transportation, and other costs of services	1,570,050	974,835	934,958
Fuel, supplies, and expenses	324,380	250,221	316,047
Depreciation and amortization	124,221	118,391	112,466
Other	129,571	129,850	126,146
Asset impairment			26,514
Total consolidated operating expenses	3,699,081	2,841,885	2,924,540
Gain on sale of subsidiaries	6,923
Gain on sale of property and equipment	$ 8,520	$ 2,376	$ 5,247

SCHEDULE II - VALUATION AND Q_2

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowance for doubtful accounts receivable and revenue adjustments
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	$ 7,851	$ 5,448	$ 7,380
Additions, Charged to Costs and Expenses	1,466	4,327	1,223
Additions, Charged to Other Accounts	7,788	1,887	(245)
Deductions	3,879	3,811	2,910
Balance at End of Period	13,226	7,851	5,448
Allowance for other accounts receivable
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	660	476	806
Additions, Charged to Costs and Expenses	30	(14)	(330)
Additions, Charged to Other Accounts		198
Balance at End of Period	690	660	476
Allowance for deferred tax assets
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	1,284	668	53
Deductions	(912)	(616)	(615)
Balance at End of Period	$ 2,196	$ 1,284	$ 668