Asset Quality (Impaired Loans) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Financing Receivable, Impaired [Line Items]
Unpaid principal balance - Impaired loans with an associated allowance	$ 2,424	$ 2,462
Unpaid principal balance - Impaired loans without an associated allowance	1,018	1,102
Unpaid principal balance - Total impaired loans	3,442	3,564
Recorded investment - Impaired loans with an associated allowance	2,002	2,161
Recorded investment - Impaired loans without an associated allowance	696	731
Recorded investment - Total impaired loans	2,698	2,892
Associated Allowance - Total impaired loans	374	463
Average recorded investment - Impaired loans with an associated allowance	2,085	2,249
Average recorded investment - Impaired loans without an associated allowance	716	908
Average recorded investment - Total impaired loans	2,801	3,157
Specific ALLL reserve for TDRs	309	386	$ 436
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid principal balance - Impaired loans with an associated allowance	398	432
Unpaid principal balance - Impaired loans without an associated allowance	45	106
Recorded investment - Impaired loans with an associated allowance	305	318
Recorded investment - Impaired loans without an associated allowance	38	84
Associated Allowance - Total impaired loans	59	74
Average recorded investment - Impaired loans with an associated allowance	305	360
Average recorded investment - Impaired loans without an associated allowance	73	133
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Unpaid principal balance - Impaired loans with an associated allowance	367	418
Unpaid principal balance - Impaired loans without an associated allowance	183	249
Recorded investment - Impaired loans with an associated allowance	196	262
Recorded investment - Impaired loans without an associated allowance	157	187
Associated Allowance - Total impaired loans	41	65
Average recorded investment - Impaired loans with an associated allowance	230	283
Average recorded investment - Impaired loans without an associated allowance	171	276
Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Unpaid principal balance - Impaired loans with an associated allowance	1,006	1,021
Unpaid principal balance - Impaired loans without an associated allowance	421	403
Recorded investment - Impaired loans with an associated allowance	982	984
Recorded investment - Impaired loans without an associated allowance	147	145
Associated Allowance - Total impaired loans	189	215
Average recorded investment - Impaired loans with an associated allowance	984	986
Average recorded investment - Impaired loans without an associated allowance	144	134
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Unpaid principal balance - Impaired loans with an associated allowance	478	397
Unpaid principal balance - Impaired loans without an associated allowance	369	344
Recorded investment - Impaired loans with an associated allowance	362	420
Recorded investment - Impaired loans without an associated allowance	354	315
Associated Allowance - Total impaired loans	58	75
Average recorded investment - Impaired loans with an associated allowance	398	422
Average recorded investment - Impaired loans without an associated allowance	328	365
Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Unpaid principal balance - Impaired loans with an associated allowance	117	130
Recorded investment - Impaired loans with an associated allowance	117	130
Associated Allowance - Total impaired loans	26	32
Average recorded investment - Impaired loans with an associated allowance	124	147
Other Consumer [Member]
Financing Receivable, Impaired [Line Items]
Unpaid principal balance - Impaired loans with an associated allowance	58	64
Recorded investment - Impaired loans with an associated allowance	40	47
Associated Allowance - Total impaired loans	1	2
Average recorded investment - Impaired loans with an associated allowance	$ 44	$ 51