Loans - Loan Portfolio Composition and Aging Analysis (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Current	$ 274,269	$ 270,655
Total	$ 280,466	$ 277,340
Current, percentage of total loans	97.79%	97.59%
Percentage of total loans	100.00%	100.00%
Unamortized premiums and discounts, deferred fees and costs	$ 1,400	$ 1,400
Accrued interest receivable	1,300	1,200
Credit Card
Financing Receivable, Past Due [Line Items]
Current	111,240	112,148
Total	113,962	114,772
Consumer Banking
Financing Receivable, Past Due [Line Items]
Current	77,011	74,028
Total	80,330	77,646
Consumer Banking | Auto
Financing Receivable, Past Due [Line Items]
Current	75,319	72,221
Total	78,604	75,779
Consumer Banking | Retail banking
Financing Receivable, Past Due [Line Items]
Current	1,692	1,807
Total	1,726	1,867
Commercial Banking
Financing Receivable, Past Due [Line Items]
Current	86,018	84,479
Total	86,174	84,922
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Current	34,272	35,100
Total	34,354	35,262
Commercial Banking | Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Current	51,746	49,379
Total	$ 51,820	$ 49,660
30-59 days
Financing Receivable, Past Due [Line Items]
Past due, percentage of total loans	1.13%	1.26%
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 3,152	$ 3,501
30-59 days | Credit Card
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	829	850
30-59 days | Consumer Banking
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	2,277	2,420
30-59 days | Consumer Banking | Auto
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	2,268	2,385
30-59 days | Consumer Banking | Retail banking
Financing Receivable, Past Due [Line Items]
Total	9	35
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	9	35
30-59 days | Commercial Banking
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	46	231
30-59 days | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	31	92
30-59 days | Commercial Banking | Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 15	$ 139
60-89 days
Financing Receivable, Past Due [Line Items]
Past due, percentage of total loans	0.51%	0.60%
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 1,442	$ 1,656
60-89 days | Credit Card
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	608	578
60-89 days | Consumer Banking
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	817	940
60-89 days | Consumer Banking | Auto
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	812	933
60-89 days | Consumer Banking | Retail banking
Financing Receivable, Past Due [Line Items]
Total	5	7
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	5	7
60-89 days | Commercial Banking
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	17	138
60-89 days | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	9	35
60-89 days | Commercial Banking | Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 8	$ 103
Greater than 90 days
Financing Receivable, Past Due [Line Items]
Past due, percentage of total loans	0.57%	0.55%
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 1,603	$ 1,528
Greater than 90 days | Credit Card
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	1,285	1,196
Greater than 90 days | Consumer Banking
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	225	258
Greater than 90 days | Consumer Banking | Auto
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	205	240
Greater than 90 days | Consumer Banking | Retail banking
Financing Receivable, Past Due [Line Items]
Total	20	18
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	20	18
Greater than 90 days | Commercial Banking
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	93	74
Greater than 90 days | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	42	35
Greater than 90 days | Commercial Banking | Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 51	$ 39
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Past due total, percentage of total loans	2.21%	2.41%
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 6,197	$ 6,685
Financial Asset, Past Due | Credit Card
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	2,722	2,624
Financial Asset, Past Due | Consumer Banking
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	3,319	3,618
Financial Asset, Past Due | Consumer Banking | Auto
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	3,285	3,558
Financial Asset, Past Due | Consumer Banking | Retail banking
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	34	60
Financial Asset, Past Due | Commercial Banking
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	156	443
Financial Asset, Past Due | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	82	162
Financial Asset, Past Due | Commercial Banking | Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	74	281
Domestic credit card: | Credit Card
Financing Receivable, Past Due [Line Items]
Current	105,484	106,312
Total	107,987	108,723
Domestic credit card: | 30-59 days | Credit Card
Financing Receivable, Past Due [Line Items]
Total	754	773
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	754	773
Domestic credit card: | 60-89 days | Credit Card
Financing Receivable, Past Due [Line Items]
Total	558	528
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	558	528
Domestic credit card: | Greater than 90 days | Credit Card
Financing Receivable, Past Due [Line Items]
Total	1,191	1,110
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	1,191	1,110
Domestic credit card: | Financial Asset, Past Due | Credit Card
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	2,503	2,411
International card businesses: | Credit Card
Financing Receivable, Past Due [Line Items]
Current	5,756	5,836
Total	5,975	6,049
International card businesses: | 30-59 days | Credit Card
Financing Receivable, Past Due [Line Items]
Total	75	77
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	75	77
International card businesses: | 60-89 days | Credit Card
Financing Receivable, Past Due [Line Items]
Total	50	50
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	50	50
International card businesses: | Greater than 90 days | Credit Card
Financing Receivable, Past Due [Line Items]
Total	94	86
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	94	86
International card businesses: | Financial Asset, Past Due | Credit Card
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 219	$ 213