CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
OPERATING ACTIVITIES
Net income	$ 166,895	$ 274,436	$ 296,381
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	215,812	214,153	179,787
Stock-based compensation expense	8,177	7,860	8,075
Loss on disposition of assets, net	9,371	6,099	3,831
Deferred income tax (benefit) provision	(13,060)	4,821	77,074
Excess tax benefits for share-based payments	(3,178)	(2,724)	(3,371)
(Increase) decrease in assets:
Accounts receivable	(49,959)	73,809	(167,312)
Income taxes receivable	1,692	9,295	9,817
Inventories	14,078	(40,354)	(36,511)
Prepaid expenses	1,519	(2,284)	(2,783)
Other current assets	1,114	26,189	(30,524)
Other non-current assets	(1,881)	(6,415)	294
(Increase) decrease in liabilities:
Accounts payable	14,062	(4,929)	30,102
Income taxes payable	(6,428)	(4,277)	4,917
Accrued payroll and related expenses	4,585	(1,627)	9,799
Accrued insurance expenses	(80)	408	603
Accrued state, local and other taxes	(2,324)	2,260	2,078
Other accrued expenses	(1,548)	1,412	958
Pension liabilities	3,183	(589)	1,249
Long-term accrued insurance expenses	(175)	1,400	511
Other long-term liabilities	3,769	990	1,032
Net cash provided by operating activities	365,624	559,933	386,007
INVESTING ACTIVITIES
Capital expenditures	(201,681)	(328,936)	(416,400)
Increased ownership interest in subsidiary		(6,211)
Proceeds from sale of assets	11,071	19,309	24,763
Purchase of business	(17,044)
Net cash used for investing activities	(207,654)	(315,838)	(391,637)
FINANCING ACTIVITIES
Payment of dividends	(87,789)	(114,069)	(47,327)
Borrowings from notes payable to banks	686,700	844,050	940,850
Repayments of notes payable to banks	(740,400)	(940,350)	(858,800)
Debt issue costs for notes payable to banks			(415)
Excess tax benefits for share-based payments	3,178	2,724	3,371
Cash paid for common stock purchased and retired	(25,122)	(30,224)	(34,419)
Proceeds received upon exercise of stock options		544	728
Net cash (used for) provided by financing activities	(163,433)	(237,325)	3,988
Net (decrease) increase in cash and cash equivalents	(5,463)	6,770	(1,642)
Cash and cash equivalents at beginning of year	14,163	7,393	9,035
Cash and cash equivalents at end of year	$ 8,700	$ 14,163	$ 7,393