Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Revenues:
Total revenues	$ 196,627	$ 378,351	$ 487,553	$ 792,236
Segment operating income (loss):
Total operating loss	(3,021,654)	(99,439)	(3,107,997)	(146,501)
Interest expense, net	(74,851)	(73,402)	(153,087)	(138,834)
Gain (loss) on extinguishment of debt	0	11,397	58,626	(2,492)
Other income (loss), net	0	978	0	(778)
Loss before income tax benefit	(3,096,505)	(160,466)	(3,202,458)	(288,605)
Income tax benefit	(641,441)	(9,075)	(667,198)	(45,036)
Net loss	(2,455,064)	(151,391)	(2,535,260)	(243,569)
Depreciation and depletion:
Total depreciation and depletion	51,478	69,816	110,660	146,240
Capital expenditures:
Total capital expenditures	30,965	31,195	48,332	43,476
Segment assets:
Total segment assets	2,127,712		2,127,712		$ 5,331,364
U.S. Operations
Segment operating income (loss):
Income tax benefit	(3,600)
Operating segment | U.S. Operations
Revenues:
Total revenues	188,311	298,685	439,322	629,349
Segment operating income (loss):
Total operating loss	(78,163)	(30,409)	(124,926)	(24,539)
Depreciation and depletion:
Total depreciation and depletion	34,915	37,694	72,065	76,760
Capital expenditures:
Total capital expenditures	29,706	29,490	46,373	39,741
Segment assets:
Total segment assets	995,426		995,426		1,122,850
Operating segment | Canadian and U.K. Operations
Revenues:
Total revenues	7,486	79,044	46,500	160,621
Segment operating income (loss):
Total operating loss	(2,928,775)	(66,426)	(2,963,096)	(119,044)
Depreciation and depletion:
Total depreciation and depletion	15,964	31,509	37,421	68,219
Capital expenditures:
Total capital expenditures	1,020	1,435	1,361	2,044
Segment assets:
Total segment assets	562,994		562,994		3,538,073
Other
Revenues:
Total revenues	830	622	1,731	2,266
Segment operating income (loss):
Total operating loss	(14,716)	(2,604)	(19,975)	(2,918)
Depreciation and depletion:
Total depreciation and depletion	599	613	1,174	1,261
Capital expenditures:
Total capital expenditures	239	$ 270	598	$ 1,691
Segment assets:
Total segment assets	$ 569,292		$ 569,292		$ 670,441