Loans and Related Allowance for Credit Losses (Analysis of Loan Portfolio) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	$ 237,013	$ 241,928
Percentage of total loans, past due	100.00%	100.00%
Unearned income, unamortized deferred fees and costs on originated loans, and premiums or discounts on purchased loans	$ 1,400	$ 1,300
Collateral Dependent
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	1,400	1,500
Other Assets
Financing Receivable, Past Due [Line Items]
Accrued interest on loan portfolio	700	700
Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	$ 233,156	$ 237,716
Percentage of total loans, past due	98.38%	98.27%
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	$ 485	$ 620
Percentage of total loans, past due	0.20%	0.26%
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	$ 182	$ 234
Percentage of total loans, past due	0.08%	0.10%
90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	$ 479	$ 509
Percentage of total loans, past due	0.20%	0.21%
Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	$ 1,146	$ 1,363
Percentage of total loans, past due	0.48%	0.56%
Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	$ 2,138	$ 2,286
Percentage of total loans, past due	0.90%	0.94%
Fair Value Option Nonaccrual Loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 573	$ 563
Percentage of total loans, nonaccrual, past due	0.24%	0.23%
Total commercial
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	$ 164,506	$ 167,203
Total commercial | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	163,566	166,075
Total commercial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	113	143
Total commercial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	15	32
Total commercial | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	63	30
Total commercial | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	191	205
Total commercial | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	749	923
Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	72,507	74,725
Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	69,590	71,641
Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	372	477
Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	167	202
Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	416	479
Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	955	1,158
Total consumer | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	1,389	1,363
Total consumer | Fair Value Option Nonaccrual Loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	573	563
Commercial and industrial | Total commercial
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	129,798	132,073
Commercial and industrial | Total commercial | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	129,130	131,245
Commercial and industrial | Total commercial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	80	106
Commercial and industrial | Total commercial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	13	26
Commercial and industrial | Total commercial | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	63	30
Commercial and industrial | Total commercial | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	156	162
Commercial and industrial | Total commercial | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	512	666
Commercial real estate | Total commercial
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	28,319	28,716
Commercial real estate | Total commercial | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	28,085	28,485
Commercial real estate | Total commercial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	12	6
Commercial real estate | Total commercial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	1	1
Commercial real estate | Total commercial | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	13	7
Commercial real estate | Total commercial | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	221	224
Equipment lease financing | Total commercial
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	6,389	6,414
Equipment lease financing | Total commercial | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	6,351	6,345
Equipment lease financing | Total commercial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	21	31
Equipment lease financing | Total commercial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	1	5
Equipment lease financing | Total commercial | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	22	36
Equipment lease financing | Total commercial | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	16	33
Home equity
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	23,493	24,088
Home equity | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	23,493	24,088
Home equity | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	22,706	23,318
Home equity | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	43	50
Home equity | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	20	21
Home equity | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	63	71
Home equity | Total consumer | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	656	645
Home equity | Total consumer | Fair Value Option Nonaccrual Loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	68	54
Residential real estate
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	22,418	22,560
Residential real estate | Government insured or guaranteed loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	930	922
Residential real estate | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	22,418	22,560
Residential real estate | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	20,862	20,945
Residential real estate | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	162	181
Residential real estate | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	73	78
Residential real estate | Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	275	319
Residential real estate | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	510	578
Residential real estate | Total consumer | Total Past Due | Government insured or guaranteed loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	400	400
Residential real estate | Total consumer | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	541	528
Residential real estate | Total consumer | Fair Value Option Nonaccrual Loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	505	509
Automobile | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	13,584	14,218
Automobile | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	13,305	13,863
Automobile | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	76	134
Automobile | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	19	34
Automobile | Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	6	12
Automobile | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	101	180
Automobile | Total consumer | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	178	175
Credit card | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	5,675	6,215
Credit card | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	5,561	6,074
Credit card | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	31	43
Credit card | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	24	30
Credit card | Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	52	60
Credit card | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	107	133
Credit card | Total consumer | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	7	8
Education
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	2,842	2,946
Education | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	2,842	2,946
Education | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	2,692	2,785
Education | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	49	55
Education | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	25	29
Education | Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	76	77
Education | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	150	161
Education | Total consumer | Total Past Due | Government insured or guaranteed loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	100	200
Other consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	4,495	4,698
Other consumer | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	4,495	4,698
Other consumer | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	4,464	4,656
Other consumer | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	11	14
Other consumer | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	6	10
Other consumer | Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	7	11
Other consumer | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	24	35
Other consumer | Total consumer | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	$ 7	$ 7