Convertible Preferred Stock Convertible Preferred Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Features of Convertible Preferred Stock [Abstract]
Liquidation preference per share	$ 1,000.00
Shares Outstanding (actual number)	200,000	200,000	525,000
Conversion rate per share	74.4500	73.1904	73.1904
Conversion price	$ 13.43	$ 13.66	$ 13.66
Preferred shares purchased (actual number)		303,526
Payments for repurchase of preferred stock including transaction costs		$ 267.6
Sale of preferred stock price per share		$ 869.86
Payment of unpaid dividends on preferred stock purchased		1.9
Preferred stock purchased carrying value		293.3
Benefit from preferred stock repurchased	0	25.7	0
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs		10.2
Preferred stock declared, annual dividends per share	$ 52.50
Preferred stock dividends	$ (11.6)	$ (15.6)	$ (27.6)