Investments - Debt Maturities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Embedded derivatives - fixed maturities
Available-for-sale Securities Including Securities Pledged [Line Items]
One year or less, Amortized Cost	$ 582
One year or less, Fair Value	587
After one year through five years, Amortized Cost	3,644
After one year through five years, Fair Value	3,784
After five years through ten years, Amortized Cost	5,631
After five years through ten years, Fair Value	5,944
After ten years, Amortized Cost	8,056
After ten years, Fair Value	9,077
Amortized Cost	24,974	$ 24,898
Fixed maturities, including securities pledged, Fair Value	26,700	25,034
Mortgage-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Without single maturity date, Amortized Cost	5,633
Without single maturity date, Fair Value	5,876
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Without single maturity date, Amortized Cost	1,428
Without single maturity date, Fair Value	1,432
Amortized Cost	1,428	1,230
Fixed maturities, including securities pledged, Fair Value	$ 1,432	$ 1,208