Investments (Rollforward Of Cumulative Credit-Related Other-Than-Temporary Impairment Charges Recognized In Earnings) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 0.8		$ 0.8
Adoption of guidance now encompassed in ASC Topic 810*	0	[1]	(18.0)	[1]
No OTTI has been previously recognized	0		0
OTTI has been previously recongized	0		0
Ending balance	0.8		0.8
Underlying investment in CLO's	(50.4)
Credit related OTTI related to CLO's					(18.0)
Previously Adjusted [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance					18.8
Ending balance			$ 0.8		$ 18.8

[1] The company adopted guidance now encompassed in ASC Topic 810 on January 1, 2010, resulting in the consolidation of CLOs for which the company has an underlying investment of $50.4 million at December 31, 2011 (before consolidation). Of the $18.8 million cumulative credit-related OTTI balance at January 1, 2010, $18.0 million relates to CLOs that were consolidated into the company's Consolidated Balance Sheet, resulting in the elimination of our equity interest.