Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Revenues:
Total	$ 455,796	$ 611,974	$ 1,388,635	$ 1,921,111
Segment operating income (loss):
Total operating loss	(59,081)	(1,071,765)	(153,254)	(919,716)
Less interest expense, net	(63,529)	(30,432)	(168,482)	(88,985)
Other income (loss), net	4,886	(943)	4,277	(13,855)
Loss from continuing operations before income tax benefit	(117,724)	(1,103,140)	(317,459)	(1,022,556)
Income tax benefit	(17,000)	(41,184)	(132,799)	(27,972)
Loss from continuing operations	(100,724)	(1,061,956)	(184,660)	(994,584)
Impairment Charges:
Impairment charges		1,106,715		1,106,715
Depreciation and depletion:
Total depreciation and depletion	82,986	82,560	232,496	223,512
Capital expenditures:
Total capital expenditures	28,484	85,284	108,735	331,340
Identifiable assets by segment:
Total identifiable assets	5,840,512		5,840,512		5,768,420
U.S. Operations
Revenues:
Total	337,269	483,615	997,503	1,402,526
Segment operating income (loss):
Total operating loss	(8,008)	(22,228)	22,368	191,998
Impairment Charges:
Impairment charges		114,281		114,281
Depreciation and depletion:
Total depreciation and depletion	53,060	44,789	131,722	130,635
Capital expenditures:
Total capital expenditures	24,741	41,670	90,945	121,633
Identifiable assets by segment:
Total identifiable assets	1,372,266		1,372,266		1,603,745
Canadian and U.K. operations
Revenues:
Total	119,367	127,905	390,684	515,901
Segment operating income (loss):
Total operating loss	(48,022)	(1,036,690)	(163,135)	(1,074,924)
Impairment Charges:
Impairment charges		992,434		992,434
Depreciation and depletion:
Total depreciation and depletion	29,383	37,305	99,235	91,976
Capital expenditures:
Total capital expenditures	2,867	43,419	16,412	205,776
Identifiable assets by segment:
Total identifiable assets	3,722,676		3,722,676		3,728,817
Other
Revenues:
Total	(840)	454	448	2,684
Segment operating income (loss):
Total operating loss	(3,051)	(12,847)	(12,487)	(36,790)
Depreciation and depletion:
Total depreciation and depletion	543	466	1,539	901
Capital expenditures:
Total capital expenditures	876	195	1,378	3,931
Identifiable assets by segment:
Total identifiable assets	$ 745,570		$ 745,570		$ 435,858