Loans - Wholesale Loan Portfolio, Geographic Distribution and Delinquency (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Financing Receivable, Past Due [Line Items]
Total retained loans	$ 1,285,370	$ 1,280,870	$ 1,265,941
Wholesale
Financing Receivable, Past Due [Line Items]
Total retained loans	687,890	672,472	$ 671,952
Wholesale | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	3,517	2,346
Wholesale | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	681,546	667,341
Wholesale | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	2,409	2,447
Wholesale | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	418	338
Wholesale | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	559,670	549,636
Wholesale | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	128,220	122,836
Wholesale | Secured by real estate
Financing Receivable, Past Due [Line Items]
Total retained loans	163,391	162,338
Wholesale | Secured by real estate | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	974	401
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	161,784	161,314
Wholesale | Secured by real estate | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	392	473
Wholesale | Secured by real estate | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	241	150
Wholesale | Secured by real estate | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	160,217	159,499
Wholesale | Secured by real estate | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	3,174	2,839
Wholesale | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total retained loans	164,248	167,166
Wholesale | Commercial and industrial | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	1,733	1,221
Wholesale | Commercial and industrial | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	161,815	164,899
Wholesale | Commercial and industrial | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	635	884
Wholesale | Commercial and industrial | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	65	162
Wholesale | Commercial and industrial | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	125,103	127,638
Wholesale | Commercial and industrial | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	39,145	39,528
Wholesale | Other
Financing Receivable, Past Due [Line Items]
Total retained loans	360,251	342,968
Wholesale | Other | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	810	724
Wholesale | Other | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	357,947	341,128
Wholesale | Other | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	1,382	1,090
Wholesale | Other | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	112	26
Wholesale | Other | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	274,350	262,499
Wholesale | Other | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	$ 85,901	$ 80,469