Investments - Debt Maturities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Embedded derivatives - fixed maturities
Available-for-sale Securities Including Securities Pledged [Line Items]
One year or less, Amortized Cost	$ 740
One year or less, Fair Value	743
After one year through five years, Amortized Cost	3,393
After one year through five years, Fair Value	3,382
After five years through ten years, Amortized Cost	5,628
After five years through ten years, Fair Value	5,657
After ten years, Amortized Cost	7,907
After ten years, Fair Value	8,728
Fixed maturities, including securities pledged, Amortized Cost	25,837	$ 25,336
Fixed maturities, including securities pledged, Fair Value	$ 26,472	$ 27,460
Mortgage-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Percent Collateralized Mortgage Backed Securities including Interest-Only Strip or Principal-Only Strip	48.90%	48.40%
Without single maturity date, Amortized Cost	$ 6,691
Without single maturity date, Fair Value	6,622
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Without single maturity date, Amortized Cost	1,478
Without single maturity date, Fair Value	1,340
Fixed maturities, including securities pledged, Amortized Cost	1,478	$ 1,472
Fixed maturities, including securities pledged, Fair Value	$ 1,340	$ 1,474