Income Taxes (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Deferred tax assets - current:
Derivative instruments current, net	$ 0	$ 255
Incentive compensation-other, net	9,329	4,627
Net deferred tax assets - current	9,329	4,882
Deferred Tax Liabilities Current [Abstract]
Derivative instruments, net	(82,709)	(47,567)
Deferred Tax Assets Liabilities Net Current	(73,380)	(42,685)
Deferred Tax Assets Noncurrent Before Valuation Allowances	28,239	29,620
Deferred tax assets - non - current [Abstract]
U.S. federal tax credit carryforwards	13,280	13,714
Capital loss carryforwards	1,929	0
Derivative instruments, net	0	1,161
Incentive compensation/other, net	13,030	14,745
Net deferred tax assets - non-current	24,618	27,928
Deferred Tax Liabilities - non current [Abstract]
Property and equipment	659,040	448,298
Derivative instruments	0	0
Other	587	341
Net non-current tax liabilities	(659,627)	(448,639)
Net non-current tax liability	(635,009)	(420,711)
Foreign Tax Credit (FTC) [Member]
Deferred Tax Liabilities Current [Abstract]
Valuation allowance	(1,692)	(1,692)
Capital Loss Carryforwards [Member]
Deferred Tax Liabilities Current [Abstract]
Valuation allowance	$ (1,929)