Loan Sale and Servicing Activities and Variable Interest Entities (Principal Balance, Delinquent Loans (Loans 90 Days or More Past Due), and Net Charge-Offs Related to Serviced Loans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Residential mortgage loans held for sale
Total principal balance	$ 37,861		$ 37,861		$ 39,016
Delinquent loans	271		271		329
Net charge-offs			1	$ 2
Commercial mortgage loans held for sale
Total principal balance	53,473		53,473		57,492
Delinquent loans	91		91		$ 89
Net charge-offs	$ 30	$ 14	$ 91	$ 18