Fair Values of Assets and Liabilities (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended														3 Months Ended
	Mar. 31, 2012 Residential Non-agency Prime [Member]	Mar. 31, 2011 Residential Non-agency Prime [Member]	Mar. 31, 2012 Residential Non-agency Non-Prime [Member]	Mar. 31, 2011 Residential Non-agency Non-Prime [Member]	Mar. 31, 2012 Commercial Mortgage-backed Non-Agency Securities [Member]	Mar. 31, 2011 Commercial Mortgage-backed Non-Agency Securities [Member]	Mar. 31, 2012 Collateralized Loan Obligations [Member]	Mar. 31, 2011 Collateralized Loan Obligations [Member]	Mar. 31, 2012 Other [Member]	Mar. 31, 2011 Other [Member]	Mar. 31, 2012 Corporate Debt Securities [Member]	Dec. 31, 2011 Corporate Debt Securities [Member]	Mar. 31, 2011 Corporate Debt Securities [Member]	Dec. 31, 2010 Corporate Debt Securities [Member]	Mar. 31, 2012 Available for Sale Securities [Member]	Mar. 31, 2011 Available for Sale Securities [Member]	Mar. 31, 2012 Mortgage servicing rights [Member]	Mar. 31, 2011 Mortgage servicing rights [Member]	Mar. 31, 2012 Net derivative assets and liabilities [Member]	Mar. 31, 2011 Net derivative assets and liabilities [Member]
Changes in fair value for all assets and liabilities measured at fair value
Beginning of period balance	$ 803	$ 1,103	$ 802	$ 947	$ 42	$ 50	$ 120	$ 135	$ 117	$ 133	$ 9	$ 9	$ 9	$ 9	$ 1,893	$ 2,377	$ 1,519	$ 1,837	$ 1,228	$ 851
Net Gains (Losses) Included in Net Income		2	(3)				5	4	3	4					5	10	(56)	16	331	43
Net Gains (Losses) Included in Other Comprehensive Income (Loss)	16	46	37	51		1	(1)	9	1	3					53	110
Purchases																	13	7
Sales	(48)	(115)		(12)											(48)	(127)			0	(1)
Principal Payments	(38)	(73)	(30)	(39)	(2)	(1)	(5)	(6)	(9)	(7)					(84)	(126)
Issuances																	261	213
Settlements																			(470)	(146)
End of Period Balance	733	963	806	947	40	50	119	142	112	133	9	9	9	9	1,819	2,244	1,737	2,073	1,089	747
Net Change in Unrealized Gains (Losses) Relating to Assets Still Held at End of Period	$ 13	$ 38	$ 37	$ 51			$ (1)	$ 9	$ 1	$ 3					$ 50	$ 101	$ (56)	$ 16	$ (461)	$ (139)