Debt (Interest Rate Swaps) (Details) (Interest Rate Swaps [Member], USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Interest Rate Swaps [Member]
Principal amount of note	$ 1,000,000,000		$ 1,000,000,000
Mark-to-market adjustments	41,500,000		41,500,000		42,300,000
Reduction of interest expense	$ 7,700,000	$ 7,000,000	$ 15,400,000	$ 14,800,000