CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
OPERATING ACTIVITIES
Net income (loss)	$ (1,060,375)	$ 363,598	$ 385,797
Less (income) loss from discontinued operations	(5,180)		3,628
Income (loss) from continuing operations	(1,065,555)	363,598	389,425
Adjustments to reconcile net income (loss) from continuing operations to net cash flows provided by (used in) operating activities:
Depreciation and depletion	316,232	230,681	98,702
Deferred income tax provision (benefit)	(132,220)	66,803	83,174
Amortization of debt issuance costs	22,606	21,154	2,975
Excess tax benefits from stock-based compensation arrangements	(217)	(8,929)	(28,875)
Gain on initial investment in Western Coal Corp		(20,553)
Goodwill and other asset impairment charges	1,107,512
Other	(59,190)	18,764	14,433
Decrease (increase) in current assets, net of effect of business acquisitions:
Receivables	44,378	(1,605)	(65,935)
Inventories	(62,630)	(1,885)	1,966
Prepaid expenses and other current assets	11,702	18,929	13,155
Increase (decrease) in current liabilities, net of effect of business acquisitions:
Accounts payable	34,594	13,676	23,717
Accrued expenses and other current liabilities	112,695	6,233	41,413
Cash flows provided by operating activities	329,907	706,866	574,150
INVESTING ACTIVITIES
Additions to property, plant and equipment	(391,512)	(436,705)	(157,476)
Proceeds from sales of investments	13,239	27,325
Other	898	1,413	(3,414)
Cash flows used in investing activities	(377,375)	(2,840,660)	(370,854)
FINANCING ACTIVITIES
Proceeds from issuance of debt	496,510	2,350,000
Borrowings under revolving credit agreement	510,650	71,259
Repayments on revolving credit agreement	(519,453)	(61,259)
Retirements of debt	(392,851)	(290,630)	(26,972)
Dividends paid	(31,246)	(30,042)	(25,266)
Purchases of stock under stock repurchase program			(65,438)
Excess tax benefits from stock-based compensation arrangements	217	8,929	28,875
Proceeds from stock options exercised	161	8,920	17,134
Cash paid upon exercise of warrants	(11,535)
Debt issuance costs	(24,532)	(80,027)
Other	(766)	(5,203)	(3,015)
Cash flows provided by (used in) financing activities	27,155	1,971,947	(74,682)
Cash flows provided by (used in) continuing operations	(20,313)	(161,847)	128,614
CASH FLOWS FROM DISCONTINUED OPERATIONS
Cash flows used in operating activities			(6,268)
Cash flows provided by investing activities	9,500		5,066
Cash flows provided by (used in) discontinued operations	9,500		(1,202)
Effect of foreign exchange rates on cash	(1,016)	(3,668)
Net increase (decrease) in cash and cash equivalents	(11,829)	(165,515)	127,412
Cash and cash equivalents at beginning of year	128,430	293,410	165,279
Add: Cash and cash equivalents of discontinued operations at beginning of year		535	1,254
Net increase (decrease) in cash and cash equivalents	(11,829)	(165,515)	127,412
Less: Cash and cash equivalents of discontinued operations at end of year			535
Cash and cash equivalents at end of year	116,601	128,430	293,410
SUPPLEMENTAL DISCLOSURES:
Interest paid, net of capitalized interest	95,642	63,828	9,848
Income taxes paid, net of refunds	12,433	69,101	77,247
Non-Cash Financing Activities:
One-year property insurance policy financing agreement			18,947
Western Coal Corp
INVESTING ACTIVITIES
Acquisition of		(2,432,693)
FINANCING ACTIVITIES
Cash paid upon exercise of warrants	(11,500)
Acquisition of Western Coal in 2011 and HighMount in 2010:
Fair value of assets acquired		5,164,842
Less: fair value of liabilities assumed		(1,418,640)
fair value of shares of common stock issued		(1,224,126)
fair value of stock options issued and warrants		(34,765)
gain on initial investment		(20,553)
cash acquired		(34,065)
Net cash paid		2,432,693
HighMount Exploration and Production Alabama, LLC
INVESTING ACTIVITIES
Acquisition of			(209,964)
Acquisition of Western Coal in 2011 and HighMount in 2010:
Fair value of assets acquired			217,607
Less: fair value of liabilities assumed			(7,643)
Net cash paid			$ 209,964