Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Operating activties
Net income (loss)	$ (388,264)	$ 71,625
Adjustments to reconcile to cash provided by operating activities:
Depreciation, depletion and amortization	399,672	320,320
Amortization of acquired sales contracts, net	(22,561)	(5,492)
Bridge financing costs related to ICG		49,490
Net loss resulting from early retirement of debt and refinancing activities	19,042	1,958
Noncash mine closure and asset impairment costs	501,942	7,316
Goodwill impairment	115,791
Prepaid royalties expensed	19,802	26,880
Employee stock-based compensation expense	9,435	9,019
Amortization relating to financing activities	14,345	9,854
Changes in:
Receivables	102,252	(35,874)
Inventories	(16,635)	(23,716)
Coal derivative assets and liabilities	(29,523)	15,199
Accounts payable, accrued expenses and other current liabilities	(51,968)	3,742
Income taxes, net	22,048	(21,971)
Deferred income taxes	(255,530)	17,062
Other	(83,453)	25,955
Cash provided by operating activities	356,395	471,367
Investing activities
Acquisition of ICG, net of cash acquired		(2,894,339)
Change in restricted cash	6,872	(5,939)
Capital expenditures	(303,968)	(215,899)
Proceeds from dispositions of property, plant and equipment	22,624	25,133
Purchases of short term investments	(99,628)
Investments in and advances to affiliates	(12,685)	(56,827)
Purchase of noncontrolling interest	(17,500)
Additions to prepaid royalties	(9,192)	(26,135)
Cash used in investing activities	(413,477)	(3,174,006)
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		1,267,776
Payments to retire debt	(452,806)	(604,096)
Net increase (decrease) in borrowings under lines of credit and commercial paper program	(381,300)	283,096
Payments on term note	(3,500)
Net payments on other debt	(13,078)	(8,792)
Debt financing costs	(34,686)	(114,587)
Dividends paid	(36,072)	(57,470)
Issuance of common stock under incentive plans	5,131	1,628
Cash provided by (used in) financing activities	469,689	2,767,555
Increase (decrease) in cash and cash equivalents	412,607	64,916
Cash and cash equivalents, beginning of period	138,149	93,593
Cash and cash equivalents, end of period	$ 550,756	$ 158,509