CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
OPERATING ACTIVITIES
Net loss	$ (9,662)	$ (160,423)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	17,800	39,532
Stock-based compensation expense	1,539	2,097
Gain on disposition of assets, net	(1,460)	(819)
Deferred income tax benefit	(752)	(33,495)
Impairment and other non-cash charges		205,437
(Increase) decrease in assets:
Accounts receivable	(25,076)	(5,664)
Income taxes receivable	331	(10,855)
Inventories	2,800	3,286
Prepaid expenses	1,097	1,753
Other current assets	614	81
Other non-current assets	2,735	4,980
Increase (decrease) in liabilities:
Accounts payable	18,155	17,004
Income taxes payable	187	257
Accrued payroll and related expenses	4,638	182
Accrued insurance expenses	(1,046)	(448)
Accrued state, local and other taxes	1,751	1,347
Other accrued expenses	(1,611)	(2,733)
Pension liabilities	(1,788)	(5,070)
Long-term accrued insurance expenses	(1,279)	825
Other long-term liabilities	291	(2,435)
Net cash provided by operating activities	9,264	54,839
INVESTING ACTIVITIES
Capital expenditures	(11,750)	(25,019)
Proceeds from sale of assets	3,968	3,595
Net cash used for investing activities	(7,782)	(21,424)
FINANCING ACTIVITIES
Cash paid for common stock purchased and retired	(557)	(792)
Net cash used for financing activities	(557)	(792)
Net increase in cash and cash equivalents	925	32,623
Cash and cash equivalents at beginning of period	84,496	50,023
Cash and cash equivalents at end of period	85,421	82,646
Supplemental cash flows disclosure:
Income taxes refund, net	(481)	(12,281)
Supplemental disclosure of noncash investing activities:
Capital expenditures included in accounts payable	$ 5,271	$ 7,250