Investment Securities (Details 6) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Credit losses on Non-agency mortgage-backed and other debt securities
Balance at beginning of period	$ 298	$ 358
Additions to credit losses due to other-than-temporary impairments
Credit losses on securities not previously considered other-than-temporarily impaired	1	1
Decreases in expected cash flows on securities for which other-than-temporary impairment was previously recognized	8	5
Total other-than-temporary impairment on debt securities	9	6
Other changes in credit losses
Increases in expected cash flows	(6)	(7)
Realized losses (a)	(13)	(17)
Credit losses on security sales and securities expected to be sold		(1)
Balance at end of period	$ 288	$ 339