INCOME TAXES - Deferred (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Accrued expenses	$ 40,502	$ 41,757
Operating lease liabilities	33,933	19,726
Supplemental pension liabilities	103	1,091
Multiemployer pension fund withdrawal	5,409	5,546
Postretirement liabilities other than pensions	4,871	5,359
Share-based compensation	5,827	5,605
Federal and state net operating loss carryforwards	1,353	1,093
Revenue recognition	1,426
Other	1,297	1,538
Total deferred tax assets	94,721	81,715
Valuation allowance	(1,284)	(668)
Total deferred tax assets, net of valuation allowance	93,437	81,047
Deferred tax liabilities:
Amortization, depreciation, and basis differences for property, plant and equipment, and other long-lived assets	113,092	107,835
Operating lease right-of-use assets	32,923	18,703
Intangibles	7,520	7,373
Revenue recognition		669
Prepaid expenses	6,151	4,952
Total deferred tax liabilities	159,686	139,532
Net deferred tax liabilities	$ (66,249)	$ (58,485)