Variable Interest Entities and Securitization Activities - Mortgage and Asset Backed Securitization Assets (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Residential mortgages
Variable Interest Entity
UPB	$ 28,005	$ 27,594
Commercial mortgages
Variable Interest Entity
UPB	49,354	55,501
U.S. agency collateralized mortgage obligations
Variable Interest Entity
UPB	31,997	14,969
Other consumer or commercial loans
Variable Interest Entity
UPB	6,142	8,133
MABS
Variable Interest Entity
UPB	115,498	106,197
Debt and equity interests
Variable Interest Entity
Debt and Equity Interests	15,538	15,671
Debt and equity interests | Residential mortgages
Variable Interest Entity
Debt and Equity Interests	4,144	4,581
Debt and equity interests | Commercial mortgages
Variable Interest Entity
Debt and Equity Interests	3,969	4,327
Debt and equity interests | U.S. agency collateralized mortgage obligations
Variable Interest Entity
Debt and Equity Interests	5,341	3,443
Debt and equity interests | Other consumer or commercial loans
Variable Interest Entity
Debt and Equity Interests	$ 2,084	$ 3,320