CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING ACTIVITIES
Net (loss) income	$ (99,561)	$ 245,193	$ 166,895
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	275,413	233,940	215,812
Stock-based compensation expense	9,960	9,074	8,177
Loss on disposition of assets, net	6,417	15,472	9,371
Deferred income tax (benefit) provision	(33,013)	12,354	(13,060)
Excess tax benefits for share-based payments	(1,410)	(4,336)	(3,178)
(Increase) decrease in assets:
Accounts receivable	401,753	(198,021)	(49,959)
Income taxes receivable	(20,867)	(19,059)	1,692
Inventories	26,667	(29,708)	14,078
Prepaid expenses	161	2	1,519
Other current assets	(2,881)	(749)	1,114
Other non-current assets	1,768	(2,238)	(1,881)
Increase (decrease) in liabilities:
Accounts payable	(62,446)	36,421	14,062
Income taxes payable	6,695	944	(6,428)
Accrued payroll and related expenses	(33,143)	13,221	4,585
Accrued insurance expenses	(1,336)	(440)	(80)
Accrued state, local and other taxes	(3,983)	1,819	(2,324)
Other accrued expenses	(180)	(775)	(1,548)
Pension liabilities	1,021	2,219	3,183
Long-term accrued insurance expenses	1,249	(126)	(175)
Other long-term liabilities	1,508	7,550	3,769
Net cash provided by operating activities	473,792	322,757	365,624
INVESTING ACTIVITIES
Capital expenditures	(167,426)	(371,502)	(201,681)
Proceeds from sale of assets	9,843	18,707	11,071
Purchase of business			(17,044)
Investment in joint venture		(2,554)
Net cash used for investing activities	(157,583)	(355,349)	(207,654)
FINANCING ACTIVITIES
Payment of dividends	(33,602)	(91,608)	(87,789)
Borrowings from notes payable to banks	613,300	1,168,100	686,700
Repayments of notes payable to banks	(837,800)	(996,900)	(740,400)
Debt issue costs for notes payable to banks		(667)
Excess tax benefits for share-based payments	1,410	4,336	3,178
Cash paid for common stock purchased and retired	(4,093)	(49,597)	(25,122)
Net cash (used for) provided by financing activities	(260,785)	33,664	(163,433)
Net increase (decrease) in cash and cash equivalents	55,424	1,072	(5,463)
Cash and cash equivalents at beginning of year	9,772	8,700	14,163
Cash and cash equivalents at end of year	$ 65,196	$ 9,772	$ 8,700