Loans - Consumer, Excluding Credit Card Loan Portfolio (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,425,236	$ 1,408,905	$ 1,300,990
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	367,274	368,741	$ 372,892
Consumer, excluding credit card | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	301,947	303,531
Consumer, excluding credit card | Auto and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 65,327	$ 65,210