CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
OPERATING ACTIVITIES
Net income	$ 5,432	$ 112,073
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	86,809	79,410
Stock-based compensation expense	4,888	4,586
Gain on disposition of assets, net	(4,637)	(3,173)
Deferred income tax (benefit) provision	(12,579)	5,171
(Increase) decrease in assets:
Accounts receivable	(34,337)	843
Income taxes receivable	31,158	18,984
Inventories	11,701	(11,880)
Prepaid expenses	1,614	2,607
Other current assets	600	990
Other non-current assets	(3,609)	(1,113)
Increase (decrease) in liabilities:
Accounts payable	2,764	22,892
Income taxes payable	(3,647)	4,342
Accrued payroll and related expenses	(2,758)	515
Accrued insurance expenses	1,167	293
Accrued state, local and other taxes	2,753	(2,751)
Other accrued expenses	(349)	160
Pension liabilities	4,497	(4,367)
Long-term accrued insurance expenses	2,208	440
Other long-term liabilities	(245)	(818)
Net cash provided by operating activities	93,430	229,204
INVESTING ACTIVITIES
Capital expenditures	(132,253)	(149,692)
Proceeds from sale of assets	9,776	6,895
Net cash used for investing activities	(122,477)	(142,797)
FINANCING ACTIVITIES
Payment of dividends	(32,224)	(43,186)
Cash paid for common stock purchased and retired	(7,349)	(40,096)
Net cash used for financing activities	(39,573)	(83,282)
Net (decrease) increase in cash and cash equivalents	(68,620)	3,125
Cash and cash equivalents at beginning of period	116,262	91,050
Cash and cash equivalents at end of period	47,642	94,175
Supplemental cash flows disclosure:
Income taxes (refund) paid, net	(12,125)	4,977
Supplemental disclosure of noncash investing activities:
Capital expenditures included in accounts payable	$ 31,407	$ 19,727