Loans and ACL (Summary of the primary reason loan modifications were classified as restructurings) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Commercial and Industrial [Member]
Summary Of Reason Modifications Were Considered Restructurings [Line Items]
TDR Rate Modification	$ 23	$ 9	$ 38	$ 14
TDR Structure Modification	9	11	15	39
TDR Increase to Allowance	1	0	1	0
Commercial Real Estate - Other [Member]
Summary Of Reason Modifications Were Considered Restructurings [Line Items]
TDR Rate Modification	10	26	37	30
TDR Structure Modification	14	5	29	14
TDR Increase to Allowance	0	(1)	1	0
Commercial Real Estate - Residential ADC [Member]
Summary Of Reason Modifications Were Considered Restructurings [Line Items]
TDR Rate Modification	10	22	15	22
TDR Structure Modification	3	8	5	21
TDR Increase to Allowance	(2)	(2)	(2)	(2)
Commercial Other Lending Subsidiaries [Member]
Summary Of Reason Modifications Were Considered Restructurings [Line Items]
TDR Rate Modification	0	0	0	0
TDR Structure Modification	0	0	0	0
TDR Increase to Allowance	0	0	0	0
Direct Retail Lending [Member]
Summary Of Reason Modifications Were Considered Restructurings [Line Items]
TDR Rate Modification	9	10	21	16
TDR Structure Modification	3	4	5	6
TDR Increase to Allowance	1	2	2	3
Retail Revolving Credit [Member]
Summary Of Reason Modifications Were Considered Restructurings [Line Items]
TDR Rate Modification	6	7	14	15
TDR Structure Modification	0	0	0	0
TDR Increase to Allowance	1	1	3	3
Retail Residential Mortgage [Member]
Summary Of Reason Modifications Were Considered Restructurings [Line Items]
TDR Rate Modification	20	27	35	82
TDR Structure Modification	26	37	47	46
TDR Increase to Allowance	3	6	6	9
Retail Sales Finance [Member]
Summary Of Reason Modifications Were Considered Restructurings [Line Items]
TDR Rate Modification	10	1	28	3
TDR Structure Modification	11	0	16	0
TDR Increase to Allowance	1	0	2	0
Retail Other Lending Subsidiaries [Member]
Summary Of Reason Modifications Were Considered Restructurings [Line Items]
TDR Rate Modification	37	21	92	29
TDR Structure Modification	0	0	0	2
TDR Increase to Allowance	$ 6	$ 4	$ 24	$ 8