Loans and ACL (Summary of the primary reason loan modifications were classified as TDRs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Commercial and Industrial, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	$ 49	$ 23	$ 68	$ 38
TDR structure modification	10	9	29	15
TDR increase to allowance	1	1	2	1
CRE Income Producing Properties, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	5	6	13	17
TDR structure modification	6	10	11	25
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	6	14	11	35
TDR structure modification	10	7	13	9
TDR increase to allowance	0	(2)	0	(2)
Direct Retail Lending, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	8	9	19	21
TDR structure modification	1	3	3	5
TDR increase to allowance	1	1	4	2
Retail Revolving Credit, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	6	6	13	14
TDR structure modification	0	0	0	0
TDR increase to allowance	2	1	3	3
Retail Residential Mortgage-Nonguaranteed, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	19	20	51	35
TDR structure modification	8	26	17	47
TDR increase to allowance	2	3	13	6
Retail Residential Mortgage-Government Guaranteed, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	105	46	144	82
TDR structure modification	0	0	0	0
TDR increase to allowance	4	3	7	7
Retail Sales Finance, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	1	2	1	3
TDR structure modification	1	1	6	3
TDR increase to allowance	0	1	1	2
Retail Other Lending Subsidiaries, Excluding Covered [Member]
Summary Of Reason Modifications Were Considered TDRs [Line Items]
TDR rate modification	29	37	58	92
TDR structure modification	0	0	0	0
TDR increase to allowance	$ 3	$ 6	$ 8	$ 24