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	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Residential Mortgages
Total principal balance	$ 42,726	$ 43,351
Delinquent loans	569	453
Net charge-offs	4	17
Commercial Mortgages
Total principal balance	39,551	40,790
Delinquent loans	42	136
Net charge-offs	$ 179	$ 127