Business Segment Information - Segments' Total Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Segments’ total assets
Total assets	$ 2,819,627	$ 2,434,079
Operating Segments
Segments’ total assets
Total assets	2,555,486	2,209,704
ALM activities
Segments’ total assets
Total assets	1,176,071	721,806
Other
Segments’ total assets
Total assets	65,755	67,947
Elimination of segment asset allocations to match liabilities
Segments’ total assets
Total assets	$ (977,685)	$ (565,378)