Loans - Loan Portfolio Composition and Aging Analysis (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Financing Receivable, Past Due [Line Items]
Current	$ 312,251	$ 314,735
Total	$ 323,598	$ 327,775
Current, percentage of total loans	96.49%	96.02%
Percentage of total loans	100.00%	100.00%
Unamortized premiums and discounts, deferred fees and costs	$ 1,300	$ 1,200
Credit Card:
Financing Receivable, Past Due [Line Items]
Current	150,479	155,135
Total	157,189	162,508
Consumer Banking:
Financing Receivable, Past Due [Line Items]
Current	74,579	72,837
Total	78,896	78,092
Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Current	73,360	71,600
Total	77,656	76,829
Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Current	1,219	1,237
Total	1,240	1,263
Commercial Banking:
Financing Receivable, Past Due [Line Items]
Current	87,193	86,763
Total	87,513	87,175
Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Current	31,956	31,733
Total	31,971	31,903
Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Current	55,237	55,030
Total	55,542	55,272
30-59 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 4,775	$ 5,276
Delinquent Loans, percentage of total loans	1.48%	1.61%
30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 1,906	$ 2,080
30-59 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	2,754	3,162
30-59 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	2,744	3,149
30-59 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	10	13
Total	10	13
30-59 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	115	34
30-59 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1	31
30-59 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	114	3
60-89 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 2,663	$ 3,138
Delinquent Loans, percentage of total loans	0.82%	0.96%
60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 1,434	$ 1,575
60-89 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,181	1,532
60-89 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,176	1,529
60-89 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	5	3
Total	5	3
60-89 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	48	31
60-89 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	0	9
60-89 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	48	22
Greater than 90 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 3,909	$ 4,626
Delinquent Loans, percentage of total loans	1.21%	1.41%
Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 3,370	$ 3,718
Greater than 90 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	382	561
Greater than 90 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	376	551
Greater than 90 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	6	10
Total	6	10
Greater than 90 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	157	347
Greater than 90 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	14	130
Greater than 90 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	143	217
Total Delinquent Loans
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 11,347	$ 13,040
Total Delinquent Loans, percentage of total loans	3.51%	3.98%
Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 6,710	$ 7,373
Total Delinquent Loans | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	4,317	5,255
Total Delinquent Loans | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	4,296	5,229
Total Delinquent Loans | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	21	26
Total Delinquent Loans | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	320	412
Total Delinquent Loans | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	15	170
Total Delinquent Loans | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	305	242
Domestic credit card: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	143,920	148,565
Total	150,309	155,618
Domestic credit card: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,802	1,973
Total	1,802	1,973
Domestic credit card: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,363	1,503
Total	1,363	1,503
Domestic credit card: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	3,224	3,577
Total	3,224	3,577
Domestic credit card: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	6,389	7,053
International card businesses: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	6,559	6,570
Total	6,880	6,890
International card businesses: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	104	107
Total	104	107
International card businesses: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	71	72
Total	71	72
International card businesses: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	146	141
Total	146	141
International card businesses: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 321	$ 320