Consolidated Statements Of Cash Flows (USD $)	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash Flows from Operating Activities:
Consolidated net earnings	$ 68,490,000	$ 83,455,000
Adjustments to reconcile consolidated net earnings to net cash provided by operating activities:
Depreciation, depletion and amortization	129,673,000	135,946,000
Stock-based compensation expense	9,317,000	11,684,000
Gains on divestitures and sales of assets	(3,890,000)	(4,293,000)
Deferred income taxes	6,358,000	17,131,000
Excess tax benefits from stock-based compensation transactions		(1,643,000)
Other items, net	1,370,000	704,000
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable, net	(77,971,000)	(86,798,000)
Inventories, net	(4,431,000)	8,888,000
Accounts payable	25,975,000	24,898,000
Other assets and liabilities, net	24,979,000	12,639,000
Net Cash Provided by Operating Activities	179,870,000	202,611,000
Cash Flows from Investing Activities:
Additions to property, plant and equipment	(93,518,000)	(110,024,000)
Acquisitions, net	(49,930,000)	(28,107,000)
Proceeds from divestitures and sales of assets	6,178,000	4,524,000
Railcar construction advances		(8,997,000)
Repayments of railcar construction advances		8,997,000
Net Cash Used for Investing Activities	(137,270,000)	(133,607,000)
Cash Flows from Financing Activities:
Borrowings of long-term debt	460,000,000	150,000,000
Repayments of long-term debt	(445,471,000)	(369,229,000)
Debt issuance costs	(3,328,000)	(80,000)
Change in bank overdraft	(2,123,000)	(1,737,000)
Payments on capital lease obligations		(308,000)
Dividends paid	(55,232,000)	(55,157,000)
Distributions to owners of noncontrolling interests	(1,000,000)
Purchase of remaining interest in existing limited liability company	(10,394,000)
Issuances of common stock	1,465,000	2,772,000
Excess tax benefits from stock-based compensation transactions		1,643,000
Net Cash Used for Financing Activities	(56,083,000)	(272,096,000)
Net Decrease in Cash and Cash Equivalents	(13,483,000)	(203,092,000)
Cash and Cash Equivalents, beginning of period	70,323,000	263,591,000
Cash and Cash Equivalents, end of period	56,840,000	60,499,000
Noncash Investing and Financing Activities:
Issuance of notes payable for acquisition of land		450,000
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest	36,649,000	36,073,000
Cash (refunds) payments for income taxes	$ (7,831,000)	$ 3,732,000