Acquired Property Net (Held-for-Use) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Foreclosed Properties Acquired Held-for-Use [Roll Forward]
Beginning balance, January 1	$ 835	$ 889	$ 44
Transfers in from held for sale, net and additions	1,173	1,045	977
Transfers to held for sale, net	(748)	(547)	(64)
Depreciation, asset write−downs and other	(387)	(552)	(68)
Ending balance, December 31	$ 873	$ 835	$ 889