Investment Securities (Mortgage-backed Asset Securities) (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012		Dec. 31, 2011
Investment securities
Fair value investments	$ 1.3
Level 2 Inputs
Investment securities
Fair value investments	4,761,900,000		5,206,100,000		5,016,000,000		6,088,200,000
Level 2 Inputs | Government National Mortgage Association Certificates and Obligations (GNMA)
Investment securities
Fair value investments	479,700,000		1,013,400,000
Level 2 Inputs | Federal National Mortgage Association Certificates and Obligations (FNMA)
Investment securities
Fair value investments	59,800,000		74,600,000
Level 2 Inputs | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC)
Investment securities
Fair value investments	40,000,000		55,800,000
Level 2 Inputs | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Investment securities
Fair value investments	579,500,000	[1]	1,143,800,000	[1]
Level 2 Inputs | Residential Mortgage Backed Securities
Investment securities
Fair value investments	130,600,000		160,600,000
Level 2 Inputs | Commercial Mortgage Backed Securities
Investment securities
Fair value investments	296,400,000		334,100,000
Level 2 Inputs | Mortgage-backed Securities, Issued by Private Enterprises
Investment securities
Fair value investments	427,000,000		494,700,000
Level 2 Inputs | Collateralized Mortgage Backed Securities
Investment securities
Fair value investments	1,006,500,000		1,638,500,000
Level 2 Inputs | Collateralized Credit Card Securities
Investment securities
Fair value investments	299,100,000		151,400,000
Level 2 Inputs | Collateralized Auto Loans
Investment securities
Fair value investments	287,500,000		233,200,000
Level 2 Inputs | Collateralized Securities, Other
Investment securities
Fair value investments	213,400,000		50,400,000
Level 2 Inputs | Asset-backed Securities, Securitized Loans and Receivables
Investment securities
Fair value investments	800,000,000		435,000,000
Level 2 Inputs | Mortgage-backed and asset-backed securities
Investment securities
Fair value investments	1,806,500,000		2,073,500,000
Level 3 Inputs | Government National Mortgage Association Certificates and Obligations (GNMA)
Investment securities
Fair value investments	87,300,000		0
Level 3 Inputs | Federal National Mortgage Association Certificates and Obligations (FNMA)
Investment securities
Fair value investments	0		0
Level 3 Inputs | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC)
Investment securities
Fair value investments	0		0
Level 3 Inputs | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Investment securities
Fair value investments	87,300,000	[1]	0	[1]
Level 3 Inputs | Residential Mortgage Backed Securities
Investment securities
Fair value investments	0		0
Level 3 Inputs | Commercial Mortgage Backed Securities
Investment securities
Fair value investments	0		0
Level 3 Inputs | Mortgage-backed Securities, Issued by Private Enterprises
Investment securities
Fair value investments	0		0
Level 3 Inputs | Collateralized Mortgage Backed Securities
Investment securities
Fair value investments	87,300,000		0
Level 3 Inputs | Collateralized Credit Card Securities
Investment securities
Fair value investments	0		22,100,000
Level 3 Inputs | Collateralized Auto Loans
Investment securities
Fair value investments	0		0
Level 3 Inputs | Collateralized Securities, Other
Investment securities
Fair value investments	22,000,000		0
Level 3 Inputs | Asset-backed Securities, Securitized Loans and Receivables
Investment securities
Fair value investments	22,000,000		22,100,000
Level 3 Inputs | Mortgage-backed and asset-backed securities
Investment securities
Fair value investments	109,300,000		22,100,000
Fair Value
Investment securities
Fair value investments	6,622,400,000	[2],[3]	6,950,700,000	[2],[3]	6,709,100,000	[4],[5]	7,500,800,000	[4],[5]
Fair Value | Government National Mortgage Association Certificates and Obligations (GNMA)
Investment securities
Fair value investments	567,000,000		1,013,400,000
Fair Value | Federal National Mortgage Association Certificates and Obligations (FNMA)
Investment securities
Fair value investments	59,800,000		74,600,000
Fair Value | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC)
Investment securities
Fair value investments	40,000,000		55,800,000
Fair Value | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Investment securities
Fair value investments	666,800,000	[1]	1,143,800,000	[1]
Fair Value | Residential Mortgage Backed Securities
Investment securities
Fair value investments	130,600,000		160,600,000
Fair Value | Commercial Mortgage Backed Securities
Investment securities
Fair value investments	296,400,000		334,100,000
Fair Value | Mortgage-backed Securities, Issued by Private Enterprises
Investment securities
Fair value investments	427,000,000		494,700,000
Fair Value | Collateralized Mortgage Backed Securities
Investment securities
Fair value investments	1,093,800,000		1,638,500,000
Fair Value | Collateralized Credit Card Securities
Investment securities
Fair value investments	299,100,000		173,500,000
Fair Value | Collateralized Auto Loans
Investment securities
Fair value investments	287,500,000		233,200,000
Fair Value | Collateralized Securities, Other
Investment securities
Fair value investments	235,400,000		50,400,000
Fair Value | Asset-backed Securities, Securitized Loans and Receivables
Investment securities
Fair value investments	822,000,000		457,100,000
Fair Value | Mortgage-backed and asset-backed securities
Investment securities
Fair value investments	$ 1,915,800,000		$ 2,095,600,000

[1] Represents publicly traded mortgage-backed securities which carry the full faith and credit guaranty of the U.S. government (i.e., GNMA) or are guaranteed by a government sponsored entity (i.e., FNMA, FHLMC).

[2] Carrying value includes $239.7 that is classified as assets held for sale relating to discontinued operations.

[3] Excludes carrying value of $26.9 associated with other long-term investment limited partnerships accounted for using the equity method and $(0.1) related to forward contracts

[4] Carrying value includes $111.8 that is classified as assets held for sale relating to discontinued operations.

[5] Excludes carrying value of $33.0 and $34.0 at January 1, 2012 and September 30, 2012 associated with other long-term investment limited partnerships accounted for using the equity method.