Debt (Junior Convertible Subordinated Debentures) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended				3 Months Ended	12 Months Ended			24 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jul. 15, 2012	Sep. 30, 2012 Junior Subordinated Debt [Member]	Dec. 31, 2012 Junior Subordinated Debt [Member]	Dec. 31, 1997 Junior Subordinated Debt [Member]	Dec. 31, 1997 Convertible Preferred Stock [Member]	Dec. 31, 2005 Convertible Preferred Stock [Member]
Proceeds From Liquidation Of Investment In Unconsolidated Trust						$ 15,500,000
Finance subsidiary ownership percentage							100.00%
Issued shares of convertible preferred securities								10.0
Preferred Stock, Dividend Rate, Percentage								5.25%
Convertible Preferred Securities, Par Value Per Share								$ 50
Convertible Preferred Securities, Dividend Amount Per Share								2.625
Interest rate of junior subordinated debt							5.25%
Incremental Debentures Issued to Unconsolidated Subsidary							15,500,000
Junior Subordinated Debentures Owed to Unconsolidated Subsidiary, Issued							515,500,000
Preferred securities convertible into common stock								0.9865
Convertible Preferred Securities, Shares Repurchased									1.6
Convertible Preferred Securities, Shares Repurchased, Price Per Share									$ 45.27
Convertible Preferred Securities, Shares Repurchased, Amount									71,300,000
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	0	436,700,000		436,700,000
Percentage of liquidation preference payable when called								100.00%
Redemption Price As A Percentage Of Face Amount					100.00%
Losses related to extinguishments of debt	$ 10,900,000	$ 4,800,000	$ 218,600,000		$ 6,000,000