Investment Securities (Summary of OTTI Noncredit Losses Included in Accumulated Other Comprehensive Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Investment Securities Disclosure [Abstract]
Noncredit Portion Of Other Than Temporary Impairments	$ (2)	[1]	$ (87)	[1]	$ 22	[1]	$ (117)	[1]

[1] Included in accumulated other comprehensive income (loss).