Loans - Consumer, Excluding Credit Card Loan Portfolio (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,369,785	$ 1,299,590	$ 1,285,370
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	369,859	376,334	$ 377,938
Consumer, excluding credit card | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	303,836	309,513
Consumer, excluding credit card | Auto and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 66,023	$ 66,821