Loans and ACL (Schedule of Information Regarding Impaired Loans) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Impaired Loans Excluding Acquired and Loans Held For Sale [Member]
Recorded investment	$ 1,687	$ 2,512
UPB	1,872	2,838
Average recorded investment	2,257	2,686
Interest income recognized	97	99
Impaired Financing Receivable With No Related Allowance Recorded [Member] \| Commercial and Industrial [Member]
Recorded investment	87	91
UPB	136	165
Average recorded investment	138	111
Interest income recognized	2	0
Impaired Financing Receivable With No Related Allowance Recorded [Member] \| CRE Income Producing Properties [Member]
Recorded investment	18	22
UPB	25	35
Average recorded investment	36	43
Interest income recognized	0	0
Impaired Financing Receivable With No Related Allowance Recorded [Member] \| CRE Construction And Development [Member]
Recorded investment	14	19
UPB	21	42
Average recorded investment	20	41
Interest income recognized	0	0
Impaired Financing Receivable With No Related Allowance Recorded [Member] \| Commercial Other Lending Subsidiaries [Member]
Recorded investment	0
UPB	1
Average recorded investment	0
Interest income recognized	0
Impaired Financing Receivable With No Related Allowance Recorded [Member] \| Direct Retail Lending [Member]
Recorded investment	13	23
UPB	49	76
Average recorded investment	14	23
Interest income recognized	1	1
Impaired Financing Receivable With No Related Allowance Recorded [Member] \| Retail Residential Mortgage-Nonguaranteed [Member]
Recorded investment	87	144
UPB	141	237
Average recorded investment	147	129
Interest income recognized	5	4
Impaired Financing Receivable With No Related Allowance Recorded [Member] \| Retail Residential Mortgage-Government Guaranteed [Member]
Recorded investment	3	1
UPB	4	1
Average recorded investment	7	2
Interest income recognized	0	0
Impaired Financing Receivable With No Related Allowance Recorded [Member] \| Retail Sales Finance [Member]
Recorded investment	1	1
UPB	2	2
Average recorded investment	1	1
Interest income recognized	0	0
Impaired Financing Receivable With No Related Allowance Recorded [Member] \| Retail Other Lending Subsidiaries [Member]
Recorded investment	3	2
UPB	7	6
Average recorded investment	3	4
Interest income recognized	0	0
Impaired Financing Receivable With Related Allowance Recorded [Member]
Related ALLL	210	367
Impaired Financing Receivable With Related Allowance Recorded [Member] \| Commercial and Industrial [Member]
Recorded investment	247	375
UPB	254	409
Related ALLL	42	72
Average recorded investment	279	453
Interest income recognized	5	5
Impaired Financing Receivable With Related Allowance Recorded [Member] \| CRE Income Producing Properties [Member]
Recorded investment	121	172
UPB	123	174
Related ALLL	15	21
Average recorded investment	133	197
Interest income recognized	4	4
Impaired Financing Receivable With Related Allowance Recorded [Member] \| CRE Construction And Development [Member]
Recorded investment	51	75
UPB	52	76
Related ALLL	9	16
Average recorded investment	65	112
Interest income recognized	2	3
Impaired Financing Receivable With Related Allowance Recorded [Member] \| Commercial Other Lending Subsidiaries [Member]
Recorded investment	5	1
UPB	5	1
Related ALLL	1	0
Average recorded investment	4	2
Interest income recognized	0	0
Impaired Financing Receivable With Related Allowance Recorded [Member] \| Direct Retail Lending [Member]
Recorded investment	85	198
UPB	87	204
Related ALLL	24	43
Average recorded investment	95	204
Interest income recognized	5	12
Impaired Financing Receivable With Related Allowance Recorded [Member] \| Retail Revolving Credit [Member]
Recorded investment	41	48
UPB	41	48
Related ALLL	16	19
Average recorded investment	45	52
Interest income recognized	2	2
Impaired Financing Receivable With Related Allowance Recorded [Member] \| Retail Residential Mortgage-Nonguaranteed [Member]
Recorded investment	360	812
UPB	370	830
Related ALLL	36	109
Average recorded investment	700	763
Interest income recognized	31	34
Impaired Financing Receivable With Related Allowance Recorded [Member] \| Retail Residential Mortgage-Government Guaranteed [Member]
Recorded investment	358	375
UPB	358	376
Related ALLL	32	55
Average recorded investment	402	356
Interest income recognized	17	15
Impaired Financing Receivable With Related Allowance Recorded [Member] \| Retail Sales Finance [Member]
Recorded investment	20	18
UPB	21	19
Related ALLL	4	4
Average recorded investment	20	20
Interest income recognized	1	1
Impaired Financing Receivable With Related Allowance Recorded [Member] \| Retail Other Lending Subsidiaries [Member]
Recorded investment	173	135
UPB	175	137
Related ALLL	31	28
Average recorded investment	148	173
Interest income recognized	$ 22	$ 18

Loans and ACL (Schedule of Information Regarding Impaired Loans) (Details) (USD $)
In Millions, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Impaired Loans Excluding Acquired and Loans Held For Sale [Member]

Average recorded investment