Segments - Total Assets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total assets	$ 155,732	$ 169,051
Total assets, excluding assets held for sale	136,599	148,982
Assets held for sale	19,133	20,069
Noncontrolling Interest
Segment Reporting Information [Line Items]
Total assets	1,879	1,890
Total | Parent
Segment Reporting Information [Line Items]
Total assets	134,720	147,092
Operating Segments | Retirement
Segment Reporting Information [Line Items]
Total assets	106,068	118,024
Operating Segments | Investment Management
Segment Reporting Information [Line Items]
Total assets	648	745
Operating Segments | Employee Benefits
Segment Reporting Information [Line Items]
Total assets	2,642	3,117
Corporate | Parent
Segment Reporting Information [Line Items]
Total assets	$ 25,362	$ 25,206