Segment Information - Assets by Segment (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	$ 191,088	$ 146,875
Retirement Services
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	186,400	143,881
Corporate and Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	$ 4,688	$ 2,994