Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 [PerformingFinancingReceivableMember]	Dec. 31, 2011 [PerformingFinancingReceivableMember]	Sep. 30, 2012 [PerformingFinancingReceivableMember] [CommercialRealEstateOtherReceivableMember]	Dec. 31, 2011 [PerformingFinancingReceivableMember] [CommercialRealEstateOtherReceivableMember]	Sep. 30, 2012 [PerformingFinancingReceivableMember] [ResidentialPrimeFinancingReceivableMember]	Dec. 31, 2011 [PerformingFinancingReceivableMember] [ResidentialPrimeFinancingReceivableMember]	Sep. 30, 2012 [NonperformingFinancingReceivableMember]	Dec. 31, 2011 [NonperformingFinancingReceivableMember]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable					$ 59.1	$ 80.4	$ 21.1	$ 34.5	$ 38.0	$ 45.9	$ 0	$ 0
Financing receivable acquired during period	0.2	18.5	37.6	84.5
Financing receivable significant sales	0	0	0	0
Financing Receivable, Allowance for Credit Losses	$ 3		$ 3