Investments - Amortized Cost and Fair Value of Fixed Maturity Available-for-Sale Securities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	$ 569
Due after one year through five years, Amortized Cost	2,104
Due after five years through ten years, Amortized Cost	2,257
Due after ten years, Amortized Cost	11,316
Subtotal, Amortized Cost	16,246
Other securities which provide for periodic payments, Amortized Cost	8,932
Amortized Cost	25,178	$ 2,029
Due in one year or less, Fair Value	571
Due after one year through five years, Fair Value	2,188
Due after five years through ten years, Fair Value	2,360
Due after ten years, Fair Value	11,868
Subtotal, Fair Value	16,987
Other securities which provide for periodic payments, Fair Value	9,423
Total fixed maturity available-for-sale securities, Fair Value	26,410
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Other securities which provide for periodic payments, Amortized Cost	5,527
Amortized Cost	5,527
Other securities which provide for periodic payments, Fair Value	5,739
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Other securities which provide for periodic payments, Amortized Cost	2,501
Amortized Cost	2,501	$ 22
Other securities which provide for periodic payments, Fair Value	2,772
Structured hybrids
Debt Securities, Available-for-sale [Line Items]
Other securities which provide for periodic payments, Amortized Cost	26
Other securities which provide for periodic payments, Fair Value	30
Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Other securities which provide for periodic payments, Amortized Cost	878
Other securities which provide for periodic payments, Fair Value	$ 882