Investment Securities (Details 8) (USD $) In Millions, unless otherwise specified																																																																			9 Months Ended				9 Months Ended
	Sep. 30, 2011 Mortgage-backed and asset-backed securities Fair Value	Dec. 31, 2010 Mortgage-backed and asset-backed securities Fair Value	Sep. 30, 2011 Mortgage-backed and asset-backed securities Level 3 Inputs	Dec. 31, 2010 Mortgage-backed and asset-backed securities Level 3 Inputs	Sep. 30, 2011 Mortgage-backed and asset-backed securities Level 2 Inputs	Dec. 31, 2010 Mortgage-backed and asset-backed securities Level 2 Inputs	Sep. 30, 2011 Mortgage-backed securities Fair Value	Dec. 31, 2010 Mortgage-backed securities Fair Value	Sep. 30, 2011 Mortgage-backed securities Level 2 Inputs	Dec. 31, 2010 Mortgage-backed securities Level 2 Inputs	Sep. 30, 2011 Level 3 Inputs Mortgage-backed securities	Dec. 31, 2010 Level 3 Inputs Mortgage-backed securities	Sep. 30, 2011 Agency mortgage-backed securities Fair Value	Dec. 31, 2010 Agency mortgage-backed securities Fair Value	Sep. 30, 2011 Agency mortgage-backed securities Level 2 Inputs	Dec. 31, 2010 Agency mortgage-backed securities Level 2 Inputs	Sep. 30, 2011 Level 3 Inputs Agency mortgage-backed securities	Dec. 31, 2010 Level 3 Inputs Agency mortgage-backed securities	Sep. 30, 2011 GNMA Fair Value	Dec. 31, 2010 GNMA Fair Value	Sep. 30, 2011 GNMA Level 2 Inputs	Dec. 31, 2010 GNMA Level 2 Inputs	Sep. 30, 2011 Level 3 Inputs GNMA	Dec. 31, 2010 Level 3 Inputs GNMA	Sep. 30, 2011 FNMA Fair Value	Dec. 31, 2010 FNMA Fair Value	Sep. 30, 2011 FNMA Level 2 Inputs	Dec. 31, 2010 FNMA Level 2 Inputs	Sep. 30, 2011 FHLMC Fair Value	Dec. 31, 2010 FHLMC Fair Value	Sep. 30, 2011 FHLMC Level 2 Inputs	Dec. 31, 2010 FHLMC Level 2 Inputs	Sep. 30, 2011 Non-agency mortgage-backed securities 2003	Sep. 30, 2011 Non-agency mortgage-backed securities 2005	Sep. 30, 2011 Non-agency mortgage-backed securities 2006	Sep. 30, 2011 Non-agency mortgage-backed securities 2007	Sep. 30, 2011 Non-agency mortgage-backed securities 2009	Sep. 30, 2011 Non-agency mortgage-backed securities 2010	Sep. 30, 2011 Non-agency mortgage-backed securities 2011	Sep. 30, 2011 Non-agency mortgage-backed securities Fair Value	Dec. 31, 2010 Non-agency mortgage-backed securities Fair Value	Sep. 30, 2011 Non-agency mortgage-backed securities Level 2 Inputs	Dec. 31, 2010 Non-agency mortgage-backed securities Level 2 Inputs	Dec. 31, 2010 Level 3 Inputs Non-agency mortgage-backed securities	Sep. 30, 2011 Non-agency residential mortgage-backed securities (RMBS) 2003	Sep. 30, 2011 Non-agency residential mortgage-backed securities (RMBS) 2006	Sep. 30, 2011 Non-agency residential mortgage-backed securities (RMBS) 2007	Sep. 30, 2011 Non-agency residential mortgage-backed securities (RMBS) 2010	Sep. 30, 2011 Non-agency residential mortgage-backed securities (RMBS) Fair Value	Dec. 31, 2010 Non-agency residential mortgage-backed securities (RMBS) Fair Value	Sep. 30, 2011 Non-agency residential mortgage-backed securities (RMBS) Level 2 Inputs	Dec. 31, 2010 Non-agency residential mortgage-backed securities (RMBS) Level 2 Inputs	Dec. 31, 2010 Level 3 Inputs Non-agency residential mortgage-backed securities (RMBS)	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS)	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS) 2003	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS) 2005	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS) 2007	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS) 2009	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS) 2010	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS) 2011	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS) Fair Value	Dec. 31, 2010 Non-agency commercial mortgage-backed securities (CMBS) Fair Value	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS) Level 2 Inputs	Dec. 31, 2010 Non-agency commercial mortgage-backed securities (CMBS) Level 2 Inputs	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS) Super Senior	Sep. 30, 2011 Non-agency commercial mortgage-backed securities (CMBS) Senior	Sep. 30, 2011 Fixed Rate CMBS	Sep. 30, 2011 Fixed Rate CMBS Fair Value	Sep. 30, 2011 Fixed Rate CMBS Super Senior	Sep. 30, 2011 Fixed Rate CMBS Senior	Sep. 30, 2011 Floating Rate CMBS	Sep. 30, 2011 Floating Rate CMBS Fair Value	Sep. 30, 2011 Floating Rate CMBS Super Senior	Sep. 30, 2011 Floating Rate CMBS Senior	Sep. 30, 2011 Other asset-backed securities Fair Value	Dec. 31, 2010 Other asset-backed securities Fair Value	Sep. 30, 2011 Other asset-backed securities Level 2 Inputs	Dec. 31, 2010 Other asset-backed securities Level 2 Inputs	Sep. 30, 2011 Credit card receivables Fair Value	Dec. 31, 2010 Credit card receivables Fair Value	Sep. 30, 2011 Credit card receivables Level 2 Inputs	Dec. 31, 2010 Credit card receivables Level 2 Inputs	Sep. 30, 2011 Vehicle receivables Fair Value	Dec. 31, 2010 Vehicle receivables Fair Value	Sep. 30, 2011 Vehicle receivables Level 2 Inputs	Dec. 31, 2010 Vehicle receivables Level 2 Inputs	Sep. 30, 2011 Other Fair Value	Dec. 31, 2010 Other Fair Value	Sep. 30, 2011 Other Level 2 Inputs	Dec. 31, 2010 Other Level 2 Inputs	Sep. 30, 2011 Fair Value	Dec. 31, 2010 Fair Value	Sep. 30, 2011 Fair Value Prime	Sep. 30, 2011 Fair Value Non-prime	Sep. 30, 2011 Level 2 Inputs	Dec. 31, 2010 Level 2 Inputs	Sep. 30, 2011 Super Senior	Sep. 30, 2011 Super Senior Prime	Sep. 30, 2011 Super Senior Non-prime	Sep. 30, 2011 Senior	Sep. 30, 2011 Senior Prime	Sep. 30, 2011 Senior Non-prime
Mortgage-backed, Asset-backed Securities Abstract
Average basis points of subordination (as a percent)																																																																			20				55
Percentage of underlying loans reported as non-performing (as a percent)																																																						2.00%
Fair value investments	$ 2,240.6	$ 2,071.7	$ 131.9	$ 57.0	$ 2,108.7	$ 2,014.7	$ 1,905.0	$ 1,595.2	$ 1,773.1	$ 1,538.2	$ 131.9	$ 57.0	$ 1,593.5	$ 1,417.6	$ 1,461.6	$ 1,376.7	$ 131.9	$ 40.9	$ 1,268.0	$ 1,143.6	$ 1,136.1	$ 1,102.7	$ 131.9	$ 40.9	$ 268.9	$ 234.9	$ 268.9	$ 234.9	$ 56.6	$ 39.1	$ 56.6	$ 39.1	$ 6.1	$ 14.7	$ 24.3	$ 46.6	$ 11.3	$ 12.7	$ 195.8	$ 311.5	$ 177.6	$ 311.5	$ 161.5	$ 16.1	$ 3.7	$ 24.3	$ 29.5	$ 10.5	$ 68.0	$ 90.6	$ 68.0	$ 74.5	$ 16.1		$ 2.4	$ 14.7	$ 17.1	$ 11.3	$ 2.2	$ 195.8	$ 243.5	$ 87.0	$ 243.5	$ 87.0	$ 56.1	$ 187.4		$ 201.8	$ 24.3	$ 177.5		$ 41.7	$ 31.8	$ 9.9	$ 335.6	$ 476.5	$ 335.6	$ 476.5	$ 77.5	$ 248.3	$ 77.5	$ 248.3	$ 235.5	$ 228.1	$ 235.5	$ 228.1	$ 22.6	$ 0.1	$ 22.6	$ 0.1	$ 7,265.9	$ 7,901.6	$ 49.9	$ 18.1	$ 4,969.5	$ 5,477.4	$ 40.4	$ 23.2	$ 17.2	$ 27.6	$ 26.7	$ 0.9

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method.