Business Segment Information - Segments' Total Assets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Segments’ total assets
Total assets	$ 2,338,833	$ 2,281,234	$ 2,284,174
Operating Segments
Segments’ total assets
Total assets	2,118,848		2,071,107
ALM activities
Segments’ total assets
Total assets	675,886		635,353
Elimination of segment asset allocations to match liabilities
Segments’ total assets
Total assets	(531,297)		(515,007)
Other
Segments’ total assets
Total assets	$ 75,396		$ 92,721