CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
OPERATING ACTIVITIES
Net (loss) income	$ (212,192,000)	$ (87,111,000)	$ 175,402,000
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	95,309,000	172,607,000	166,789,000
Stock-based compensation expense	8,735,000	8,630,000	9,419,000
Gain on disposition of assets, net	(9,523,000)	(2,645,000)	(3,344,000)
Gain due to insurance recovery			(9,646,000)
Gain due to benefit plan financing arrangement	(891,000)	(126,000)	(1,020,000)
Deferred income tax (benefit) provision	(25,845,000)	(22,225,000)	21,395,000
Impairment and other charges	211,043,000	73,560,000
(Increase) decrease in assets:
Accounts receivable	80,769,000	81,094,000	53,982,000
Income taxes receivable	(58,798,000)	11,687,000	4,410,000
Inventories	18,076,000	20,962,000	(15,660,000)
Prepaid expenses	1,337,000	(692,000)	(778,000)
Other current assets	227,000	300,000	3,375,000
Other non-current assets	(3,819,000)	(3,024,000)	1,494,000
Increase (decrease) in liabilities:
Accounts payable	(9,130,000)	(42,241,000)	(7,754,000)
Income taxes payable	(419,000)	(3,172,000)	1,482,000
Accrued payroll and related expenses	(1,219,000)	(6,103,000)	2,193,000
Accrued insurance expenses	(2,051,000)	1,357,000	884,000
Accrued state, local and other taxes	361,000	(654,000)	(5,574,000)
Other accrued expenses	(6,541,000)	(2,089,000)	(994,000)
Pension liabilities	(3,249,000)	6,575,000	(7,862,000)
Long-term accrued insurance expenses	(2,218,000)	1,968,000	1,696,000
Other long-term liabilities	(2,004,000)	483,000	(880,000)
Net cash provided by operating activities	77,958,000	209,141,000	389,009,000
INVESTING ACTIVITIES
Capital expenditures	(65,065,000)	(250,629,000)	(242,610,000)
Proceeds from sale of assets	22,406,000	14,841,000	13,237,000
Proceeds from insurance recovery			9,646,000
Proceeds from benefit plan financing arrangement	1,566,000	507,000	2,218,000
Re-investment in benefit plan financing arrangement	(1,566,000)	(507,000)	(2,218,000)
Net cash used for investing activities	(42,659,000)	(235,788,000)	(219,727,000)
FINANCING ACTIVITIES
Payment of dividends		(32,231,000)	(101,069,000)
Cash paid for common stock purchased and retired	(826,000)	(7,361,000)	(43,001,000)
Net cash used for financing activities	(826,000)	(39,592,000)	(144,070,000)
Net increase (decrease) in cash and cash equivalents	34,473,000	(66,239,000)	25,212,000
Cash and cash equivalents at beginning of year	50,023,000	116,262,000	91,050,000
Cash and cash equivalents at end of year	$ 84,496,000	$ 50,023,000	$ 116,262,000