Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Operating activties
Net income	$ 1,409	$ 55,874
Adjustments to reconcile to cash provided by operating activities:
Depreciation, depletion and amortization	139,966	83,537
Amortization of acquired sales contracts, net	(14,017)	5,944
Prepaid royalties expensed	8,586	8,916
Employee stock-based compensation expense	4,079	5,290
Amortization relating to financing activities	4,288	2,442
Changes in:
Receivables	88,082	(53,586)
Inventories	(111,196)	(12,292)
Coal derivative assets and liabilities	(5,347)	(1,087)
Accounts payable, accrued expenses and other current liabilities	(66,222)	(38,054)
Income taxes, net	23,002	12,558
Deferred income taxes	(21,742)	(1,026)
Other	4,102	17,629
Cash provided by operating activities	54,990	86,145
Investing activities
Decrease in restricted cash	1,455
Capital expenditures	(93,271)	(38,711)
Proceeds from dispositions of property, plant and equipment	22,105	516
Purchases of investments and advances to affiliates	(5,777)	(34,419)
Additions to prepaid royalties	(8,262)	(20,915)
Cash used in investing activities	(83,750)	(93,529)
Financing activities
Payments to retire debt	(1,330)
Net increase (decrease) in borrowings under lines of credit and commercial paper program	34,000	3,681
Net proceeds on other debt	(5,993)	(5,161)
Debt financing costs	(100)	(8)
Dividends paid	(23,327)	(16,269)
Issuance of common stock under incentive plans	5,131	768
Cash provided by (used in) financing activities	8,381	(16,989)
Decrease in cash and cash equivalents	(20,379)	(24,373)
Cash and cash equivalents, beginning of period	138,149	93,593
Cash and cash equivalents, end of period	$ 117,770	$ 69,220