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
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Residential mortgage loans held for sale
Total principal balance	$ 42,285		$ 42,726
Delinquent loans	453		569
Net charge-offs	1	$ 2
Commercial mortgage loans held for sale
Total principal balance	39,615		39,551
Delinquent loans	$ 41		$ 42
Net charge-offs		$ 153