Debt (Junior Convertible Subordinated Debentures) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	12 Months Ended				24 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 1997	Dec. 31, 2005	Jul. 15, 2012
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust						$ 436,700,000
Losses on Extinguishment of Debt	(33,200,000)	0	(10,900,000)
Junior Subordinated Debt [Member]
Proceeds From Liquidation Of Investment In Unconsolidated Trust			15,500,000
Finance subsidiary ownership percentage				100.00%
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
Redemption Price As A Percentage Of Face Amount			100.00%
Losses on Extinguishment of Debt			6,000,000
Convertible Preferred Stock [Member]
Issued shares of convertible preferred securities				10.0
Preferred Stock, Dividend Rate, Percentage				5.25%
Liquidation Preference On Preferred Stock			421,200,000
Convertible Preferred Securities, Par Value Per Share				$ 50
Convertible Preferred Securities, Dividend Amount Per Share				2.625
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
Percentage of liquidation preference payable when called				100.00%