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