Business Segment Information - Segments' Total Assets (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Segments’ total assets
Total assets	$ 2,738,452	$ 2,434,079	$ 2,426,330
Operating Segments
Segments’ total assets
Total assets	2,515,107		2,218,817
ALM activities
Segments’ total assets
Total assets	1,018,385		686,301
Other
Segments’ total assets
Total assets	62,747		67,741
Elimination of segment asset allocations to match liabilities
Segments’ total assets
Total assets	$ (857,787)		$ (546,529)