Asset Quality (Impaired Loans) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	$ 2,157	$ 2,085
Unpaid principal balance - Impaired loans without an associated allowance	1,532	1,407
Unpaid principal balance - Total impaired loans	3,689	3,492
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	1,834	1,774
Recorded investment - Impaired loans without an associated allowance	986	886
Recorded investment - Total impaired loans	2,820	2,660
Associated Allowance - Total impaired loans	421	395
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	1,798	1,977
Average recorded investment - Impaired loans without an associated allowance	971	767
Average recorded investment - Total impaired loans	2,769	2,744
TDRs [Member]
Recorded Investment - Impaired Financing Receivable [Abstract]
Associated Allowance for TDRs	357	319	$ 309
Commercial [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	661	442
Unpaid principal balance - Impaired loans without an associated allowance	328	201
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	489	337
Recorded investment - Impaired loans without an associated allowance	230	118
Associated Allowance - Total impaired loans	140	84
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	395	306
Average recorded investment - Impaired loans without an associated allowance	222	87
Commercial Real Estate [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	200	254
Unpaid principal balance - Impaired loans without an associated allowance	201	206
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	97	130
Recorded investment - Impaired loans without an associated allowance	144	158
Associated Allowance - Total impaired loans	27	35
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	110	197
Average recorded investment - Impaired loans without an associated allowance	152	168
Home Equity [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	919	978
Unpaid principal balance - Impaired loans without an associated allowance	471	464
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	875	909
Recorded investment - Impaired loans without an associated allowance	215	206
Associated Allowance - Total impaired loans	196	216
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	904	965
Average recorded investment - Impaired loans without an associated allowance	200	158
Residential Real Estate [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	246	272
Unpaid principal balance - Impaired loans without an associated allowance	509	512
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	245	264
Recorded investment - Impaired loans without an associated allowance	389	396
Associated Allowance - Total impaired loans	31	35
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	258	359
Average recorded investment - Impaired loans without an associated allowance	389	346
Credit Card [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	104	108
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	104	108
Associated Allowance - Total impaired loans	26	24
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	106	118
Other Consumer [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	27	31
Unpaid principal balance - Impaired loans without an associated allowance	23	24
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	24	26
Recorded investment - Impaired loans without an associated allowance	8	8
Associated Allowance - Total impaired loans	1	1
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	25	32
Average recorded investment - Impaired loans without an associated allowance	$ 8	$ 8