Income Taxes (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets - current:
Incentive compensation-other, net	$ 6,468	$ 9,329
Deferred Tax Assets Valuation Allowance Net Current	(6,468)	0
Net deferred tax assets - current	0	9,329
Deferred Tax Liabilities Current [Abstract]
Derivative instruments, net	0	(82,709)
Deferred Tax Assets Liabilities Net Current	0	73,380
Deferred tax assets - non - current [Abstract]
Property and equipment	350,978	0
Deferred gain on sale	55,329	0
U.S. federal tax credit carryforwards	4,870	13,280
Capital loss carryforwards	0	1,929
Net operating loss carryforwards	17,755	150
Incentive compensation/other, net	15,104	12,880
Deferred tax assets noncurrent before valuation allowances	444,036	28,239
Valuation allowance	(443,300)	(3,621)
Net deferred tax assets - non-current	736	24,618
Deferred Tax Liabilities - non current [Abstract]
Property and equipment	0	659,040
Other	736	587
Net non-current tax liabilities	736	659,627
Net non-current tax liability	$ 0	$ 635,009