Loans - Wholesale Loan Portfolio, Geographic Distribution and Delinquency (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025
Financing Receivable, Past Due [Line Items]
Total retained loans	$ 1,425,236	$ 1,408,905	$ 1,300,990
Wholesale
Financing Receivable, Past Due [Line Items]
Total retained loans	818,839	792,367	$ 704,714
Wholesale | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	4,524	4,398
Wholesale | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	812,298	784,998
Wholesale | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	1,728	2,913
Wholesale | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	289	58
Wholesale | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	643,584	626,060
Wholesale | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	175,255	166,307
Wholesale | Secured by real estate
Financing Receivable, Past Due [Line Items]
Total retained loans	166,189	165,545
Wholesale | Secured by real estate | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	1,743	1,678
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	163,743	163,189
Wholesale | Secured by real estate | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	648	636
Wholesale | Secured by real estate | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	55	42
Wholesale | Secured by real estate | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	162,987	162,378
Wholesale | Secured by real estate | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	3,202	3,167
Wholesale | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total retained loans	186,001	174,403
Wholesale | Commercial and industrial | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	2,157	1,954
Wholesale | Commercial and industrial | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	183,279	171,227
Wholesale | Commercial and industrial | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	366	1,220
Wholesale | Commercial and industrial | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	199	2
Wholesale | Commercial and industrial | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	141,523	131,945
Wholesale | Commercial and industrial | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	44,478	42,458
Wholesale | Other
Financing Receivable, Past Due [Line Items]
Total retained loans	466,649	452,419
Wholesale | Other | Criticized nonaccrual
Financing Receivable, Past Due [Line Items]
Total retained loans	624	766
Wholesale | Other | Current and less than 30 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	465,276	450,582
Wholesale | Other | 30–89 days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	714	1,057
Wholesale | Other | 90 or more days past due and still accruing
Financing Receivable, Past Due [Line Items]
Total retained loans	35	14
Wholesale | Other | Total U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	339,074	331,737
Wholesale | Other | Total non-U.S.
Financing Receivable, Past Due [Line Items]
Total retained loans	$ 127,575	$ 120,682