Debt (Interest Rate Swaps) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Mark-to-market adjustments	$ 41.3		$ 41.3		$ 35.8
Reduction of interest expense	4.9	7.6	16.7	24.1
Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge	5.7		5.7		15.8
Interest Rate Swaps [Member]
Principal amount of note	$ 250.0		$ 250.0