Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Revenues:
Total revenues	$ 290,926	$ 413,885
Operating income (loss):
Total operating loss	(86,343)	(47,062)
Interest expense, net	(78,236)	(65,432)
Gain (loss) on extinguishment of debt	58,626	(13,889)
Other loss	0	(1,756)
Loss before income tax benefit	(105,953)	(128,139)
Income tax benefit	(25,757)	(35,961)
Net loss	(80,196)	(92,178)
Depreciation and depletion:
Total depreciation and depletion	59,182	76,424
Capital expenditures:
Total capital expenditures	17,367	12,281
Segment assets:
Total segment assets	5,202,437		5,331,364
Operating segment | U.S. Operations
Revenues:
Total revenues	251,011	330,664
Operating income (loss):
Total operating loss	(46,763)	5,870
Depreciation and depletion:
Total depreciation and depletion	37,150	39,066
Capital expenditures:
Total capital expenditures	16,667	10,251
Segment assets:
Total segment assets	1,082,624		1,122,850
Operating segment | Canadian and U.K. Operations
Revenues:
Total revenues	39,014	81,577
Operating income (loss):
Total operating loss	(34,321)	(52,618)
Depreciation and depletion:
Total depreciation and depletion	21,457	36,710
Capital expenditures:
Total capital expenditures	341	609
Segment assets:
Total segment assets	3,466,709		3,538,073
Other
Revenues:
Total revenues	901	1,644
Operating income (loss):
Total operating loss	(5,259)	(314)
Depreciation and depletion:
Total depreciation and depletion	575	648
Capital expenditures:
Total capital expenditures	359	1,421
Segment assets:
Total segment assets	653,104		670,441
Accumulated Deficit
Operating income (loss):
Net loss	$ (80,196)