Investment Securities (Non-agency Residential Mortgage-backed Securities) (Details) (USD $)	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Fair value
Investment securities
Fair value investments	$ 7,581,300,000	[1],[2]	$ 8,346,800,000	[1],[2],[3],[4]	$ 7,901,600,000	[3]
Residential | Fair value
Investment securities
Fair value investments	160,600,000		83,100,000
Residential | Prime | Fair value
Investment securities
Fair value investments	160,100,000
Residential | Non-prime | Fair value
Investment securities
Fair value investments	500,000
Residential | Sub-prime | Fair value
Investment securities
Fair value investments	0
Residential | Super Senior
Investment securities
Fair value investments	9,700,000	[5]
Residential | Super Senior | Prime
Investment securities
Fair value investments	9,700,000	[5]
Residential | Super Senior | Non-prime
Investment securities
Fair value investments	0	[5]
Residential | Super Senior | Sub-prime
Investment securities
Fair value investments	0	[5]
Residential | Senior
Investment securities
Fair value investments	150,900,000	[6]
Residential | Senior | Prime
Investment securities
Fair value investments	150,400,000	[6]
Residential | Senior | Non-prime
Investment securities
Fair value investments	500,000	[6]
Residential | Senior | Sub-prime
Investment securities
Fair value investments	0	[6]
Residential | Subordinate
Investment securities
Fair value investments	0	[7]
Residential | Subordinate | Prime
Investment securities
Fair value investments	0	[7]
Residential | Subordinate | Non-prime
Investment securities
Fair value investments	0	[7]
Residential | Subordinate | Sub-prime
Investment securities
Fair value investments	$ 0	[7]

[1] Excludes carrying value of $33.0 and $35.0 at January 1, 2012 and December 31, 2012 associated with other long-term investments accounted for using the equity method and $(0.1) at December 31, 2012 related to currency forward contracts.

[2] Carrying value includes $111.8 and $338.1 at January 1, 2012 and December 31, 2012 that is classified as assets held for sale relating to discontinued operations.

[3] Excludes carrying value of $33.0 and $41.9 at December 31, 2011 and January 1, 2011 associated with other long-term investment limited partnerships accounted for using the equity method.

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

[5] At issuance, Super Senior were rated AAA by Standard & Poor’s, Aaa by Moody’s or AAA by Fitch Ratings (“Fitch”) and were senior to other AAA or Aaa bonds.

[6] At issuance, Senior were rated AAA by Standard & Poor’s, Aaa by Moody’s or AAA by Fitch and were senior to non-AAA or non-Aaa bonds.

[7] At issuance, Subordinate were not rated AAA by Standard & Poor’s, Aaa by Moody’s or AAA by Fitch and were junior to AAA or Aaa bonds.