Debt (Junior Convertible Subordinated Debentures) (Details) (USD $) In Millions, unless otherwise specified			3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Junior Subordinated Debt [Member]	Mar. 31, 2012 Convertible Preferred Stock [Member]
Finance subsidiary ownership percentage			100.00%
Issued shares of convertible preferred securities				10.0
Preferred Stock, Dividend Rate, Percentage				5.25%
Interest rate of junior subordinated debt			5.25%
Preferred securities convertible into common stock				0.9865
Preferred securities issued unconditionally guarantees				8.4
Percentage of liquidation preference payable when called				100.00%
Liquidation preference on preferred stock				$ 421.2
Maturity date of junior convertible subordinated debentures			Dec. 01, 2027
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	$ 436.7	$ 436.7