CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
OPERATING ACTIVITIES
Net income	$ 167,556	$ 129,252
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	171,382	160,706
Stock-based compensation expense	7,115	6,397
Loss on disposition of assets, net	11,321	5,665
Deferred income tax benefit	(35,508)	(10,579)
Excess tax benefits for share-based payments	(4,378)	(3,157)
(Increase) decrease in assets:
Accounts receivable	(154,687)	(2,677)
Income taxes receivable	(983)	(7,697)
Inventories	(27,746)	12,392
Prepaid expenses	3,494	5,646
Other current assets	(180)	1,095
Other non-current assets	(1,701)	(585)
Increase (decrease) in liabilities:
Accounts payable	53,170	10,924
Income taxes payable	558	(6,260)
Accrued payroll and related expenses	4,841	1,273
Accrued insurance expenses	(546)	(272)
Accrued state, local and other taxes	5,607	1,536
Other accrued expenses	38	(1,502)
Pension liabilities	1,218	2,121
Long-term accrued insurance expenses	(143)	589
Other long-term liabilities	5,846	(1,330)
Net cash provided by operating activities	206,274	303,537
INVESTING ACTIVITIES
Capital expenditures	(237,473)	(159,854)
Proceeds from sale of assets	14,980	8,578
Net cash used for investing activities	(222,493)	(151,276)
FINANCING ACTIVITIES
Payment of dividends	(68,822)	(65,923)
Borrowings from notes payable to banks	826,800	500,700
Repayments of notes payable to banks	(728,100)	(556,300)
Debt issue costs for notes payable to banks	(667)
Excess tax benefits for share-based payments	4,378	3,157
Cash paid for common stock purchased and retired	(17,548)	(25,121)
Net cash provided by (used for) financing activities	16,041	(143,487)
Net (decrease) increase in cash and cash equivalents	(178)	8,774
Cash and cash equivalents at beginning of period	8,700	14,163
Cash and cash equivalents at end of period	8,522	22,937
Supplemental cash flows disclosure:
Interest paid, net of amounts capitalized	836	1,145
Income taxes paid, net	136,647	106,728
Supplemental disclosure of noncash investing activities:
Capital expenditures included in accounts payable	$ 29,495	$ 19,987