Business Segment Information - Segments' Total Assets (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Segments’ total assets
Total assets	$ 2,377,164	$ 2,354,507	$ 2,328,478
Operating Segments
Segments’ total assets
Total assets	2,198,484		2,127,522
ALM activities
Segments’ total assets
Total assets	671,751		659,849
Elimination of segment asset allocations to match liabilities
Segments’ total assets
Total assets	(566,787)		(543,322)
Other
Segments’ total assets
Total assets	$ 73,716		$ 84,429