Loans - Consumer, Excluding Credit Card Loan Portfolio (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 1,264,093	$ 1,280,870	$ 1,084,850
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	389,592	397,275	$ 300,447
Consumer, excluding credit card | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	319,984	326,409
Consumer, excluding credit card | Auto and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained loans	$ 69,608	$ 70,866