Convertible Preferred Stock Convertible Preferred Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Features of Convertible Preferred Stock [Abstract]
Convertible preferred stock, interest rate, stated percentage	5.25%	5.25%
Liquidation preference per share	$ 1,000.00	$ 1,000.00
Shares outstanding (actual number)	200,000	200,000	200,000	221,474
Conversion rate per share	76.2197	76.2197	74.4500	73.1904
Conversion price	$ 13.12	$ 13.12	$ 13.43	$ 13.66
Conversion shares	16,900,000	16,900,000	16,500,000	16,200,000
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	0	25.7
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)	$ (11.6)	$ (15.6)
Preferred stock, quarterly dividend amount per share	$ 13.125