Segments - Total Assets (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total assets	$ 166,934	$ 169,051
Total assets, excluding assets held for sale	147,011	148,982
Assets held for sale	19,923	20,069
Noncontrolling Interest
Segment Reporting Information [Line Items]
Total assets	1,615	1,890
Total | Parent
Segment Reporting Information [Line Items]
Total assets	145,396	147,092
Operating Segments | Retirement
Segment Reporting Information [Line Items]
Total assets	116,471	118,024
Operating Segments | Investment Management
Segment Reporting Information [Line Items]
Total assets	690	745
Operating Segments | Employee Benefits
Segment Reporting Information [Line Items]
Total assets	2,893	3,117
Corporate | Parent
Segment Reporting Information [Line Items]
Total assets	$ 25,342	$ 25,206