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, 2016	Mar. 31, 2015	Dec. 31, 2015
Residential Mortgages [Member]
Total principal balance	$ 71,275		$ 72,898
Delinquent loans	1,693		1,923
Net charge-offs	26	$ 32
Commercial Mortgages [Member]
Total principal balance	51,369		53,789
Delinquent loans	1,051		1,057
Net charge-offs	912	107
Home Equity Loans Lines [Member]
Total principal balance	2,683		2,806
Delinquent loans	896		$ 904
Net charge-offs	$ 7	$ 7