Goodwill and Other Intangible Assets - Key Economic Assumptions (Details 5) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Goodwill and Intangible Assets Disclosure [Abstract]
Weighted-average prepayment speed assumption (CPR)	13.04%	18.07%
Impact on fair value of 10% adverse change	$ (517)	$ (585)
Impact on fair value of 20% adverse change	(1,009)	(1,118)
Weighted-average option adjusted spread	7.61%	7.83%
Impact on fair value of 100 basis points adverse change	(306)	(269)
Impact on fair value of 200 basis points adverse change	$ (591)	$ (518)