Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Revenues:
Total Revenues	$ 378,351	$ 441,496	$ 792,236	$ 932,839
Segment operating income (loss):
Total operating loss	(99,439)	(30,553)	(146,501)	(94,173)
Less interest expense, net	(73,402)	(52,985)	(138,834)	(98,952)
Gain (loss) on extinguishment of debt	11,397		(2,492)	(6,001)
Other income (loss)	978	(714)	(778)	(609)
Loss before income tax benefit	(160,466)	(84,252)	(288,605)	(199,735)
Income tax benefit	(9,075)	(49,760)	(45,036)	(115,799)
Net loss	(151,391)	(34,492)	(243,569)	(83,936)
Depreciation and depletion:
Total depreciation and depletion	69,816	68,320	146,240	149,510
Capital expenditures:
Total capital expenditures	31,195	46,224	43,476	80,251
Segment assets:
Total Segment assets	5,461,898		5,461,898		5,590,860
Operating segment | U.S. Operations
Revenues:
Total Revenues	298,685	321,009	629,349	660,234
Segment operating income (loss):
Total operating loss	(30,409)	37,333	(24,539)	30,376
Depreciation and depletion:
Total depreciation and depletion	37,694	31,189	76,760	78,662
Capital expenditures:
Total capital expenditures	29,490	38,803	39,741	66,204
Segment assets:
Total Segment assets	1,230,287		1,230,287		1,265,255
Operating segment | Canadian and U.K. operations
Revenues:
Total Revenues	79,044	119,873	160,621	271,317
Segment operating income (loss):
Total operating loss	(66,426)	(66,347)	(119,044)	(115,113)
Depreciation and depletion:
Total depreciation and depletion	31,509	36,620	68,219	69,852
Capital expenditures:
Total capital expenditures	1,435	7,231	2,044	13,545
Segment assets:
Total Segment assets	3,667,691		3,667,691		3,687,925
Other
Revenues:
Total Revenues	622	614	2,266	1,288
Segment operating income (loss):
Total operating loss	(2,604)	(1,539)	(2,918)	(9,436)
Depreciation and depletion:
Total depreciation and depletion	613	511	1,261	996
Capital expenditures:
Total capital expenditures	270	190	1,691	502
Segment assets:
Total Segment assets	$ 563,920		$ 563,920		$ 637,680