Asset Quality (Impaired Loans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	$ 2,085	$ 2,462
Unpaid principal balance - Impaired loans without an associated allowance	1,407	1,102
Unpaid principal balance - Total impaired loans	3,492	3,564
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	1,774	2,161
Recorded investment - Impaired loans without an associated allowance	886	731
Recorded investment - Total impaired loans	2,660	2,892
Associated Allowance - Total impaired loans	395	463
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	1,977	2,249
Average recorded investment - Impaired loans without an associated allowance	767	908
Average recorded investment - Total impaired loans	2,744	3,157
TDRs [Member]
Recorded Investment - Impaired Financing Receivable [Abstract]
Associated Allowance for TDRs	319	386	$ 470
Commercial [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	442	432
Unpaid principal balance - Impaired loans without an associated allowance	201	106
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	337	318
Recorded investment - Impaired loans without an associated allowance	118	84
Associated Allowance - Total impaired loans	84	74
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	306	360
Average recorded investment - Impaired loans without an associated allowance	87	133
Commercial Real Estate [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	254	418
Unpaid principal balance - Impaired loans without an associated allowance	206	249
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	130	262
Recorded investment - Impaired loans without an associated allowance	158	187
Associated Allowance - Total impaired loans	35	65
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	197	283
Average recorded investment - Impaired loans without an associated allowance	168	276
Home Equity [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	978	1,021
Unpaid principal balance - Impaired loans without an associated allowance	464	403
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	909	984
Recorded investment - Impaired loans without an associated allowance	206	145
Associated Allowance - Total impaired loans	216	215
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	965	986
Average recorded investment - Impaired loans without an associated allowance	158	134
Residential Real Estate [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	272	397
Unpaid principal balance - Impaired loans without an associated allowance	512	344
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	264	420
Recorded investment - Impaired loans without an associated allowance	396	315
Associated Allowance - Total impaired loans	35	75
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	359	422
Average recorded investment - Impaired loans without an associated allowance	346	365
Credit Card [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	108	130
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	108	130
Associated Allowance - Total impaired loans	24	32
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	118	147
Other Consumer [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	31	64
Unpaid principal balance - Impaired loans without an associated allowance	24
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	26	47
Recorded investment - Impaired loans without an associated allowance	8
Associated Allowance - Total impaired loans	1	2
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	32	$ 51
Average recorded investment - Impaired loans without an associated allowance	$ 8