Loans - Wholesale Loan Portfolio, Geographic Distribution and Delinquency (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Financing Receivable, Past Due [Line Items]
Total retained loans	$ 1,273,047	$ 1,280,870	$ 1,255,688
Wholesale
Financing Receivable, Past Due [Line Items]
Total retained loans	674,152	672,472	$ 668,145
Wholesale | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	3,289	2,346
Wholesale | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	667,989	667,341
Wholesale | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	2,749	2,447
Wholesale | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	125	338
Wholesale | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	551,175	549,636
Wholesale | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	122,977	122,836
Wholesale | Secured by real estate
Financing Receivable, Past Due [Line Items]
Total retained loans	163,886	162,338
Wholesale | Secured by real estate | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	864	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	162,166	161,314
Wholesale | Secured by real estate | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	813	473
Wholesale | Secured by real estate | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	43	150
Wholesale | Secured by real estate | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	160,858	159,499
Wholesale | Secured by real estate | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	3,028	2,839
Wholesale | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total retained loans	166,698	167,166
Wholesale | Commercial and industrial | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	1,620	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	164,281	164,899
Wholesale | Commercial and industrial | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	734	884
Wholesale | Commercial and industrial | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	63	162
Wholesale | Commercial and industrial | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	128,139	127,638
Wholesale | Commercial and industrial | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	38,559	39,528
Wholesale | Other
Financing Receivable, Past Due [Line Items]
Total retained loans	343,568	342,968
Wholesale | Other | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	805	724
Wholesale | Other | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	341,542	341,128
Wholesale | Other | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	1,202	1,090
Wholesale | Other | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	19	26
Wholesale | Other | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	262,178	262,499
Wholesale | Other | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	$ 81,390	$ 80,469