Investment Securities (Summary of OTTI Noncredit Losses Included in Accumulated Other Comprehensive Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Investment Securities Disclosure [Abstract]
Noncredit Portion Of Other Than Temporary Impairments	$ 2	[1]	$ (34)	[1]	$ 24	[1]	$ (30)	[1]

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