Loans and ACL (Changes in Carrying Amount and Accretable Yield for Covered Loans) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Purchased Impaired Loans [Member]
Accretable yield for purchased loans, beginning balance	$ 187	$ 264
Accretion	(85)	(149)
Other, net	56	72
Accretable yield for purchased loans, ending balance	158	187
Carrying amount of loans, beginning balance	863	1,400
Accretion	85	149
Payments received, net	(316)	(686)
Carrying amount of loans, ending balance	632	863
Outstanding UPB at end of period	941	1,266
Purchased Nonimpaired Loans [Member]
Accretable yield for purchased loans, beginning balance	351	617
Accretion	(139)	(301)
Other, net	58	35
Accretable yield for purchased loans, ending balance	270	351
Carrying amount of loans, beginning balance	1,172	1,894
Accretion	139	301
Payments received, net	(518)	(1,023)
Carrying amount of loans, ending balance	793	1,172
Outstanding UPB at end of period	$ 1,027	$ 1,516