Loans - Wholesale Loan Portfolio, Geographic Distribution and Delinquency (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024
Financing Receivable, Past Due [Line Items]
Total retained loans	$ 1,369,785	$ 1,299,590	$ 1,285,370
Wholesale
Financing Receivable, Past Due [Line Items]
Total retained loans	764,451	690,396	$ 687,890
Wholesale | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	4,740	3,942
Wholesale | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	757,313	683,244
Wholesale | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	1,944	2,938
Wholesale | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	454	272
Wholesale | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	611,626	564,912
Wholesale | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	152,825	125,484
Wholesale | Secured by real estate
Financing Receivable, Past Due [Line Items]
Total retained loans	164,371	162,432
Wholesale | Secured by real estate | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	1,535	1,439
Wholesale | Secured by real estate | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	162,473	159,949
Wholesale | Secured by real estate | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	304	918
Wholesale | Secured by real estate | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	59	126
Wholesale | Secured by real estate | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	161,145	159,209
Wholesale | Secured by real estate | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	3,226	3,223
Wholesale | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total retained loans	179,585	166,790
Wholesale | Commercial and industrial | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	2,405	1,760
Wholesale | Commercial and industrial | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	176,350	164,104
Wholesale | Commercial and industrial | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	577	868
Wholesale | Commercial and industrial | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	253	58
Wholesale | Commercial and industrial | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	134,153	127,626
Wholesale | Commercial and industrial | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	45,432	39,164
Wholesale | Other
Financing Receivable, Past Due [Line Items]
Total retained loans	420,495	361,174
Wholesale | Other | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	800	743
Wholesale | Other | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	418,490	359,191
Wholesale | Other | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	1,063	1,152
Wholesale | Other | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	142	88
Wholesale | Other | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	316,328	278,077
Wholesale | Other | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	$ 104,167	$ 83,097