Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Operating activties
Net income (loss)	$ (434,015)	$ 62,504
Adjustments to reconcile to cash provided by operating activities:
Depreciation, depletion and amortization	272,834	180,773
Amortization of acquired sales contracts, net	(18,468)	7,206
Bridge financing costs related to ICG		49,490
Net loss resulting from early retirement of debt and refinancing activities	19,042	250
Noncash mine closure and asset impairment costs	501,942	7,316
Goodwill Impairment	115,791
Prepaid royalties expensed	16,551	19,491
Employee stock-based compensation expense	7,014	7,071
Amortization relating to financing activities	8,948	5,093
Changes in:
Receivables	52,291	(25,329)
Inventories	(80,199)	(31,476)
Coal derivative assets and liabilities	(37,985)	4,902
Accounts payable, accrued expenses and other current liabilities	(64,965)	8,912
Income taxes, net	22,869	(15,186)
Deferred income taxes	(272,094)	18,177
Other	(14,248)	15,006
Cash provided by operating activities	95,308	314,200
Investing activities
Acquisition of ICG, net of cash acquired		(2,910,380)
Change in restricted cash	4,582	(74,814)
Capital expenditures	(202,073)	(107,725)
Proceeds from dispositions of property, plant and equipment	22,551	1,411
Purchases of investments and advances to affiliates	(9,292)	(38,059)
Additions to prepaid royalties	(8,634)	(25,212)
Cash used in investing activities	(192,866)	(3,154,779)
Financing activities
Proceeds from the issuance of senior notes		2,000,000
Proceeds from term note	1,386,000
Proceeds from the issuance of common stock, net		1,249,407
Payments to retire debt	(452,654)	(307,984)
Change in restricted cash		(260,663)
Net increase (decrease) in borrowings under lines of credit and commercial paper program	(391,300)	303,096
Net payments on other debt	(11,164)	(8,845)
Debt financing costs	(34,381)	(112,334)
Dividends paid	(29,696)	(34,192)
Issuance of common stock under incentive plans	5,131	846
Cash provided by (used in) financing activities	471,936	2,829,331
Increase (decrease) in cash and cash equivalents	374,378	(11,248)
Cash and cash equivalents, beginning of period	138,149	93,593
Cash and cash equivalents, end of period	$ 512,527	$ 82,345