Asset Quality (Impaired Loans) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	$ 2,134	$ 2,085
Unpaid principal balance - Impaired loans without an associated allowance	1,554	1,407
Unpaid principal balance - Total impaired loans	3,688	3,492
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	1,787	1,774
Recorded investment - Impaired loans without an associated allowance	1,040	886
Recorded investment - Total impaired loans	2,827	2,660
Associated Allowance - Total impaired loans	425	395
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	1,781	1,977
Average recorded investment - Impaired loans without an associated allowance	963	767
Average recorded investment - Total impaired loans	2,744	2,744
TDRs [Member]
Recorded Investment - Impaired Financing Receivable [Abstract]
Associated Allowance for TDRs	310	319	$ 342
Commercial [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	468	442
Unpaid principal balance - Impaired loans without an associated allowance	416	201
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	359	337
Recorded investment - Impaired loans without an associated allowance	316	118
Associated Allowance - Total impaired loans	134	84
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	348	306
Average recorded investment - Impaired loans without an associated allowance	217	87
Commercial Real Estate [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	218	254
Unpaid principal balance - Impaired loans without an associated allowance	210	206
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	105	130
Recorded investment - Impaired loans without an associated allowance	156	158
Associated Allowance - Total impaired loans	30	35
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	117	197
Average recorded investment - Impaired loans without an associated allowance	157	168
Home Equity [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	1,036	978
Unpaid principal balance - Impaired loans without an associated allowance	409	464
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	929	909
Recorded investment - Impaired loans without an associated allowance	179	206
Associated Allowance - Total impaired loans	205	216
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	920	965
Average recorded investment - Impaired loans without an associated allowance	192	158
Residential Real Estate [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	274	272
Unpaid principal balance - Impaired loans without an associated allowance	495	512
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	264	264
Recorded investment - Impaired loans without an associated allowance	381	396
Associated Allowance - Total impaired loans	32	35
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	264	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	107	108
Recorded Investment - Impaired Financing Receivable [Abstract]
Recorded investment - Impaired loans with an associated allowance	106	108
Associated Allowance - Total impaired loans	23	24
Average Recorded Receivable - Impaired Financing Receivable [Abstract]
Average recorded investment - Impaired loans with an associated allowance	107	118
Other Consumer [Member]
Unpaid Principal Balance - Impaired Financing Receivable [Abstract]
Unpaid principal balance - Impaired loans with an associated allowance	31	31
Unpaid principal balance - Impaired loans without an associated allowance	24	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