CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
OPERATING ACTIVITIES
Net income	$ 39,388	$ 35,076
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	56,280	53,572
Stock-based compensation expense	2,320	2,105
Loss on disposition of assets, net	2,232	2,640
Deferred income tax benefit	(10,192)	(5,009)
Excess tax benefits for share-based payments	(4,455)	(3,232)
(Increase) decrease in assets:
Accounts receivable	(31,043)	12,325
Income taxes receivable	8,076	(4,530)
Inventories	(9,421)	8,017
Prepaid expenses	506	246
Other current assets	1,692	234
Other non-current assets	(117)	(324)
Increase (decrease) in liabilities:
Accounts payable	19,508	4,578
Income taxes payable	6,593	(5,651)
Accrued payroll and related expenses	(6,181)	(7,077)
Accrued insurance expenses	302	252
Accrued state, local and other taxes	1,503	(2,300)
Other accrued expenses	60	(1,296)
Pension liabilities	396	1,451
Long-term accrued insurance expenses	958	314
Other long-term liabilities	(537)	(2,082)
Net cash provided by operating activities	77,868	89,309
INVESTING ACTIVITIES
Capital expenditures	(40,295)	(53,040)
Proceeds from sale of assets	2,862	2,995
Net cash used for investing activities	(37,433)	(50,045)
FINANCING ACTIVITIES
Payment of dividends	(22,986)	(22,015)
Borrowings from notes payable to banks	216,400	227,600
Repayments of notes payable to banks	(188,900)	(247,000)
Debt issue costs for notes payable to banks	(667)
Excess tax benefits for share-based payments	4,455	3,232
Cash paid for common stock purchased and retired	(13,144)	(4,961)
Net cash used for financing activities	(4,842)	(43,144)
Net increase (decrease) in cash and cash equivalents	35,593	(3,880)
Cash and cash equivalents at beginning of period	8,700	14,163
Cash and cash equivalents at end of period	44,293	10,283
Supplemental cash flows disclosure:
Interest paid, net of amounts capitalized	256	26
Income taxes paid, net	19,999	37,591
Supplemental disclosure of noncash investing activities:
Capital expenditures included in accounts payable	$ 22,432	$ 32,812