Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details 1) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets
Loss carryforwards - federal	$ 27,078	$ 52,580
Loss carryforwards - state	42,625	37,175
Tax credit carryover	41,132	34,837
Business credit carryforwards	72,748	70,452
Derivative contracts	27,261	0
Stock-based compensation	10,306	23,468
Unrecognized gain and original issue discount on debt exchange	106,321	0
Other	38,834	34,236
Valuation allowance	(36,510)	(33,600)
Total deferred tax assets	329,795	219,148
Deferred tax liabilities
Property and equipment	(619,923)	(1,004,330)
Derivative contracts	0	(50,081)
Other	(3,750)	(16,826)
Total deferred tax liabilities	(623,673)	(1,071,237)
Total net deferred tax liability	$ (293,878)	$ (852,089)