Loans and ACL (Summary of the primary reason loan modifications were classified as TDRs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Commercial and Industrial, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	$ 20	$ 42	$ 88	$ 80
TDR structure modification	11	8	40	23
TDR increase to allowance	1	1	3	2
CRE Income Producing Properties, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	5	12	18	29
TDR structure modification	4	13	15	38
TDR increase to allowance	0	0	0	1
CRE Construction And Development, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	8	10	19	45
TDR structure modification	5	5	18	14
TDR increase to allowance	0	0	0	(2)
Direct Retail Lending, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	8	10	27	31
TDR structure modification	1	1	4	6
TDR increase to allowance	1	2	5	4
Retail Revolving Credit, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	6	7	19	21
TDR structure modification	0	0	0	0
TDR increase to allowance	1	0	4	3
Retail Residential Mortgage-Nonguaranteed, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	31	39	82	74
TDR structure modification	10	15	27	62
TDR increase to allowance	3	3	16	9
Retail Residential Mortgage-Government Guaranteed, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	83	23	227	105
TDR structure modification	0	0	0	0
TDR increase to allowance	3	2	10	9
Retail Sales Finance, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	0	1	1	4
TDR structure modification	5	2	11	5
TDR increase to allowance	1	1	2	3
Retail Other Lending Subsidiaries, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	34	40	92	132
TDR structure modification	0	0	0	0
TDR increase to allowance	$ 4	$ 6	$ 12	$ 30