Loans and Related Allowance for Credit Losses (Analysis of Loan Portfolio) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	$ 294,704	$ 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	$ 1,000	$ 1,300
Collateral Dependent
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	1,900	1,500
Other assets
Financing Receivable, Past Due [Line Items]
Accrued interest on loan portfolio	800	700
Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	$ 289,912	$ 237,716
Percentage of total loans, past due	98.37%	98.27%
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	$ 548	$ 620
Percentage of total loans, past due	0.19%	0.26%
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	$ 215	$ 234
Percentage of total loans, past due	0.07%	0.10%
90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	$ 527	$ 509
Percentage of total loans, past due	0.18%	0.21%
Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	$ 1,290	$ 1,363
Percentage of total loans, past due	0.44%	0.56%
Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	$ 2,779	$ 2,286
Percentage of total loans, past due	0.94%	0.94%
Fair Value Option Nonaccrual Loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 723	$ 563
Percentage of total loans, nonaccrual, past due	0.25%	0.23%
Total commercial
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	$ 199,640	$ 167,203
Total commercial | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	198,033	166,075
Total commercial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	80	143
Total commercial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	34	32
Total commercial | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	47	30
Total commercial | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	161	205
Total commercial | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	1,446	923
Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	95,064	74,725
Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	91,879	71,641
Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	468	477
Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	181	202
Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	480	479
Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	1,129	1,158
Total consumer | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	1,333	1,363
Total consumer | Fair Value Option Nonaccrual Loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	723	563
Commercial and industrial | Total commercial
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	155,300	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	154,226	131,245
Commercial and industrial | Total commercial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	72	106
Commercial and industrial | Total commercial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	27	26
Commercial and industrial | Total commercial | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	45	30
Commercial and industrial | Total commercial | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	144	162
Commercial and industrial | Total commercial | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	930	666
Commercial real estate | Total commercial
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	37,964	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	37,453	28,485
Commercial real estate | Total commercial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	5	6
Commercial real estate | Total commercial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	3	1
Commercial real estate | Total commercial | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	2
Commercial real estate | Total commercial | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	10	7
Commercial real estate | Total commercial | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	501	224
Equipment lease financing | Total commercial
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	6,376	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	6,354	6,345
Equipment lease financing | Total commercial | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	3	31
Equipment lease financing | Total commercial | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	4	5
Equipment lease financing | Total commercial | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	7	36
Equipment lease financing | Total commercial | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	15	33
Residential real estate
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	36,846	22,560
Residential real estate | Government insured or guaranteed loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	942	922
Residential real estate | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	36,846	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	35,099	20,945
Residential real estate | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	212	181
Residential real estate | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	82	78
Residential real estate | Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	337	319
Residential real estate | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	631	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	503	528
Residential real estate | Total consumer | Fair Value Option Nonaccrual Loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	613	509
Home equity
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	25,174	24,088
Home equity | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	25,174	24,088
Home equity | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	24,377	23,318
Home equity | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	44	50
Home equity | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	17	21
Home equity | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	61	71
Home equity | Total consumer | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	626	645
Home equity | Total consumer | Fair Value Option Nonaccrual Loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	110	54
Automobile | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	17,551	14,218
Automobile | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	17,239	13,863
Automobile | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	98	134
Automobile | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	20	34
Automobile | Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	3	12
Automobile | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	121	180
Automobile | Total consumer | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	191	175
Credit card | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	6,528	6,215
Credit card | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	6,401	6,074
Credit card | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	37	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	59	60
Credit card | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	120	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	2,726	2,946
Education | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	2,726	2,946
Education | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	2,591	2,785
Education | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	46	55
Education | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	22	29
Education | Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	67	77
Education | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	135	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	6,239	4,698
Other consumer | Total consumer
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	6,239	4,698
Other consumer | Total consumer | Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	6,172	4,656
Other consumer | Total consumer | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	31	14
Other consumer | Total consumer | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	16	10
Other consumer | Total consumer | 90 Days Or More Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	14	11
Other consumer | Total consumer | Total Past Due
Financing Receivable, Past Due [Line Items]
Total loans, past due	61	35
Other consumer | Total consumer | Nonperforming Loans
Financing Receivable, Past Due [Line Items]
Total loans, before allowance for credit loss	$ 6	$ 7