Loans - Loan Portfolio Composition and Aging Analysis (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Current	$ 307,794	$ 307,695
Total	$ 320,243	$ 320,472
Current, percentage of total loans	96.11%	96.01%
Percentage of total loans	100.00%	100.00%
Unamortized premiums and discounts, deferred fees and costs	$ 1,300	$ 1,400
Credit Card:
Financing Receivable, Past Due [Line Items]
Current	149,547	147,412
Total	156,651	154,547
Consumer Banking:
Financing Receivable, Past Due [Line Items]
Current	71,911	70,097
Total	76,758	75,437
Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Current	70,682	68,768
Total	75,505	74,075
Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Current	1,229	1,329
Total	1,253	1,362
Commercial Banking:
Financing Receivable, Past Due [Line Items]
Current	86,336	90,186
Total	86,834	90,488
Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Current	32,016	34,325
Total	32,199	34,446
Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Current	54,320	55,861
Total	54,635	56,042
30-59 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 5,234	$ 5,367
Delinquent Loans, percentage of total loans	1.64%	1.68%
30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 2,098	$ 2,084
30-59 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	2,908	3,283
30-59 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	2,895	3,268
30-59 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	13	15
Total	13	15
30-59 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	228	0
30-59 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	114	0
30-59 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	114	0
60-89 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 3,072	$ 3,119
Delinquent Loans, percentage of total loans	0.96%	0.97%
60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 1,544	$ 1,547
60-89 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,454	1,558
60-89 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,452	1,555
60-89 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	2	3
Total	2	3
60-89 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	74	14
60-89 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	20	14
60-89 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	54	0
Greater than 90 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 4,143	$ 4,291
Delinquent Loans, percentage of total loans	1.29%	1.34%
Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 3,462	$ 3,504
Greater than 90 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	485	499
Greater than 90 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	476	484
Greater than 90 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	9	15
Total	9	15
Greater than 90 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	196	288
Greater than 90 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	49	107
Greater than 90 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	147	181
Total Delinquent Loans
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 12,449	$ 12,777
Total Delinquent Loans, percentage of total loans	3.89%	3.99%
Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 7,104	$ 7,135
Total Delinquent Loans | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	4,847	5,340
Total Delinquent Loans | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	4,823	5,307
Total Delinquent Loans | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	24	33
Total Delinquent Loans | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	498	302
Total Delinquent Loans | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	183	121
Total Delinquent Loans | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	315	181
Domestic credit card: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	142,633	140,860
Total	149,400	147,666
Domestic credit card: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,982	1,968
Total	1,982	1,968
Domestic credit card: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,469	1,471
Total	1,469	1,471
Domestic credit card: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	3,316	3,367
Total	3,316	3,367
Domestic credit card: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	6,767	6,806
International card businesses: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	6,914	6,552
Total	7,251	6,881
International card businesses: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	116	116
Total	116	116
International card businesses: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	75	76
Total	75	76
International card businesses: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	146	137
Total	146	137
International card businesses: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 337	$ 329