CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
OPERATING ACTIVITIES
Net income (loss)	$ (5,122)	$ (201,953)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	53,754	77,582
Stock-based compensation expense	4,481	9,321
Gain on disposition of assets, net	(7,408)	(7,576)
Deferred income tax benefit	(4,385)	(35,901)
Impairment and other non-cash charges		205,299
(Increase) decrease in assets:
Accounts receivable	(71,702)	119,272
Income taxes receivable	31,922	(40,163)
Inventories	3,044	16,234
Prepaid expenses	4,754	6,309
Other current assets	140	(70)
Other non-current assets	(982)	(1,393)
Increase (decrease) in liabilities:
Accounts payable	17,562	(4,628)
Income taxes payable	(426)	1,433
Accrued payroll and related expenses	(1,282)	(1,706)
Accrued insurance expenses	1,066	(585)
Accrued state, local and other taxes	1,815	3,180
Other accrued expenses	(2,575)	(5,181)
Pension liabilities	(1,526)	(6,163)
Long-term accrued insurance expenses	1,830	137
Other long-term liabilities	1,456	(2,084)
Net cash provided by operating activities	26,416	131,364
INVESTING ACTIVITIES
Capital expenditures	(44,925)	(52,313)
Proceeds from sale of assets	15,811	17,372
Net cash used for investing activities	(29,114)	(34,941)
FINANCING ACTIVITIES
Cash paid for common stock purchased and retired	(567)	(827)
Cash paid for finance lease	(396)
Net cash used for financing activities	(963)	(827)
Net (decrease) increase in cash and cash equivalents	(3,661)	95,596
Cash and cash equivalents at beginning of period	84,496	50,023
Cash and cash equivalents at end of period	80,835	145,619
Supplemental cash flows disclosure:
Income taxes refund, net	(25,435)	(10,137)
Supplemental disclosure of noncash investing activities:
Capital expenditures included in accounts payable	$ 6,077	$ 4,992