Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other comprehensive income [Abstract]
Other Comprehensive Income (Loss), Change in Fain Value, Derivatives Qualifying as Hedges, before Tax	$ 0	$ 26,904	$ (57,613)
Other Comprehensive Income (Loss), Change in Derivative Fair Value, Derivatives Qualifying as Hedges, Tax	0	(10,093)	21,636
Other Comprehensive Income (Loss), Change in Derivative Fair Value, Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	0	16,811	(35,977)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Reclassification to Earnings, before Tax	20,707	10,608	(108,071)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Reclassification to Earnings, Tax	(7,710)	(3,967)	40,727
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Reclassification to Earnings, Net of Tax	12,997	6,641	(67,344)
Other Comprehensive Income (Loss), Minimum Pension Liability Net Adjustment, before Tax	(2,779)	(1,570)	119
Other Comprehensive Income (Loss), Minimum Pension Liability, Tax	984	590	(45)
Other Comprehensive Income (Loss), Minimum Pension Liability, Adjustment, Net of Tax	$ (1,795)	$ (980)	$ 74