Loans - Consumer, Excluding Credit Card Loan Portfolio (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,273,047	$ 1,280,870	$ 1,255,688
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	382,795	397,275	$ 396,195
Consumer, excluding credit card | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	314,843	326,409
Consumer, excluding credit card | Auto and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 67,952	$ 70,866