CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
OPERATING ACTIVITIES
Net income (loss)	$ 104,808	$ (120,139)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	127,679	171,642
Stock-based compensation expense	9,019	8,065
Gain on disposition of assets, net	(5,779)	(3,919)
Deferred income tax benefit	(28,163)	(31,677)
Excess tax benefits for share-based payments		(360)
(Increase) decrease in assets:
Accounts receivable	(206,201)	89,173
Income taxes receivable	54,033	1,488
Inventories	(4,730)	17,843
Prepaid expenses	1,134	4,436
Other current assets	(2,037)	(378)
Other non-current assets	(3,135)	(1,251)
Increase (decrease) in liabilities:
Accounts payable	47,151	(21,603)
Income taxes payable	(728)	(3,613)
Accrued payroll and related expenses	13,088	(2,067)
Accrued insurance expenses	125	636
Accrued state, local and other taxes	4,612	4,154
Other accrued expenses	(5,385)	52
Pension liabilities	2,708	(2,121)
Long-term accrued insurance expenses	783	(1,642)
Other long-term liabilities	309	(14,159)
Net cash provided by operating activities	109,291	94,560
INVESTING ACTIVITIES
Capital expenditures	(75,016)	(24,917)
Proceeds from sale of assets	10,532	7,141
Net cash used for investing activities	(64,484)	(17,776)
FINANCING ACTIVITIES
Payment of dividends	(13,026)
Debt issuance costs for notes payable to banks		(35)
Excess tax benefits for share-based payments		360
Cash paid for common stock purchased and retired	(26,724)	(3,218)
Net cash used for financing activities	(39,750)	(2,893)
Net increase in cash and cash equivalents	5,057	73,891
Cash and cash equivalents at beginning of period	131,835	65,196
Cash and cash equivalents at end of period	136,892	139,087
Supplemental cash flows disclosure:
Interest paid, net of amounts capitalized	192	373
Income taxes paid (refund), net	39,775	(39,333)
Supplemental disclosure of noncash investing activities:
Capital expenditures included in accounts payable	$ 7,552	$ 3,002