Investment Securities (Rollforward of Cumulative OTTI Credit Losses Recognized in Earnings) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended							3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Residential mortgage-backed Securities [Member] Mortgage-backed Securities Non-agency [Member]	Sep. 30, 2011 Residential mortgage-backed Securities [Member] Mortgage-backed Securities Non-agency [Member]	Sep. 30, 2012 Residential mortgage-backed Securities [Member] Mortgage-backed Securities Non-agency [Member]	Sep. 30, 2011 Residential mortgage-backed Securities [Member] Mortgage-backed Securities Non-agency [Member]	Sep. 30, 2011 Commercial Mortgage Backed Securities [Member] Mortgage-backed Securities Non-agency [Member]	Sep. 30, 2012 Commercial Mortgage Backed Securities [Member] Mortgage-backed Securities Non-agency [Member]	Jun. 30, 2012 Commercial Mortgage Backed Securities [Member] Mortgage-backed Securities Non-agency [Member]	Dec. 31, 2011 Commercial Mortgage Backed Securities [Member] Mortgage-backed Securities Non-agency [Member]	Jun. 30, 2011 Commercial Mortgage Backed Securities [Member] Mortgage-backed Securities Non-agency [Member]	Sep. 30, 2012 Asset backed [Member]	Sep. 30, 2011 Asset backed [Member]	Sep. 30, 2012 Asset backed [Member]	Sep. 30, 2011 Asset backed [Member]	Sep. 30, 2012 Other Debt Securities [Member]	Sep. 30, 2011 Other Debt Securities [Member]	Jun. 30, 2012 Other Debt Securities [Member]	Jun. 30, 2011 Other Debt Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Beginning balance	$ (1,162)	$ (1,012)	$ (1,091)	$ (955)	$ (890)	$ (761)	$ (828)	$ (709)	$ (11)	$ (6)	$ (6)	$ (6)	$ (6)	$ (252)	$ (232)	$ (244)	$ (223)	$ (13)	$ (12)	$ (14)	$ (13)
Loss where impairment was not previously recognized	(6)	(2)	(9)	(9)	(6)	(2)	(8)	(5)									(3)	(1)	(1)
Additional loss where credit impairment was previously recognized	(18)	(33)	(87)	(99)	(17)	(28)	(78)	(88)						(1)	(5)	(9)	(11)
Reduction due to credit impaired securities sold			1	16			1	11	5
Ending balance	$ (1,186)	$ (1,047)	$ (1,186)	$ (1,047)	$ (913)	$ (791)	$ (913)	$ (791)	$ (6)	$ (6)	$ (6)	$ (6)	$ (6)	$ (253)	$ (237)	$ (253)	$ (237)	$ (14)	$ (13)	$ (14)	$ (13)