Investments - Fixed Maturities and Equity Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Available-for-sale Securities Including Securities Pledged [Line Items]
Securities pledged, Amortized Cost	$ 749	$ 867
U.S. Treasuries
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	565	651
Gross Unrealized Capital Gains	129	87
Gross Unrealized Capital Losses	3	0
Embedded Derivatives	0	0
Fixed maturities including securities pledged, Fair Value	691	738
OTTI	0	0
U.S. Government agencies and authorities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	19	0
Gross Unrealized Capital Gains	0	0
Gross Unrealized Capital Losses	0	0
Embedded Derivatives	0	0
Fixed maturities including securities pledged, Fair Value	19	0
OTTI	0	0
State, municipalities and political subdivisions
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	747	754
Gross Unrealized Capital Gains	68	18
Gross Unrealized Capital Losses	0	8
Embedded Derivatives	0	0
Fixed maturities including securities pledged, Fair Value	815	764
OTTI	0	0
U.S. corporate public securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	7,103	7,908
Gross Unrealized Capital Gains	941	288
Gross Unrealized Capital Losses	13	181
Embedded Derivatives	0	0
Fixed maturities including securities pledged, Fair Value	8,031	8,015
OTTI	0	0
U.S. corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	3,776	3,686
Gross Unrealized Capital Gains	306	73
Gross Unrealized Capital Losses	16	106
Embedded Derivatives	0	0
Fixed maturities including securities pledged, Fair Value	4,066	3,653
OTTI	0	0
Foreign corporate public securities and foreign governments
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	2,417	2,551
Gross Unrealized Capital Gains	265	69
Gross Unrealized Capital Losses	3	80
Embedded Derivatives	0	0
Fixed maturities including securities pledged, Fair Value	2,679	2,540
OTTI	0	0
Foreign corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	3,171	3,235
Gross Unrealized Capital Gains	205	37
Gross Unrealized Capital Losses	1	97
Embedded Derivatives	0	0
Fixed maturities including securities pledged, Fair Value	3,375	3,175
OTTI	0	0
Residential mortgage-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	3,685	2,966
Gross Unrealized Capital Gains	125	93
Gross Unrealized Capital Losses	11	32
Embedded Derivatives	(11)	(9)
Fixed maturities including securities pledged, Fair Value	3,810	3,036
OTTI	2	3
Commercial mortgage-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	2,381	1,917
Gross Unrealized Capital Gains	122	16
Gross Unrealized Capital Losses	3	28
Embedded Derivatives	0	0
Fixed maturities including securities pledged, Fair Value	2,500	1,905
OTTI	0	0
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	1,472	1,230
Gross Unrealized Capital Gains	15	6
Gross Unrealized Capital Losses	13	28
Embedded Derivatives	0	0
Fixed maturities including securities pledged, Fair Value	1,474	1,208
OTTI	1	2
Fixed maturities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	25,336	24,898
Total fixed maturities, less securities pledged, Amortized Cost	24,587	24,031
Gross Unrealized Capital Gains	2,176	687
Total fixed maturities, less securities pledged, Gross Unrealized Capital Gains	2,091	642
Gross Unrealized Capital Losses	63	560
Total fixed maturities, less securities pledged, Gross Unrealized Capital Losses	57	530
Embedded Derivatives	(11)	(9)
Fixed maturities including securities pledged, Fair Value	27,460	25,034
Total fixed maturities, less securities pledged, Fair Value	26,632	24,152
OTTI	3	5
Impaired
Available-for-sale Securities Including Securities Pledged [Line Items]
Net unrealized gains on impaired available-for-sale securities	194	137
Collateral Pledged
Available-for-sale Securities Including Securities Pledged [Line Items]
Securities pledged, Gross Unrealized Capital Losses	828	882
Collateral Pledged | Fixed maturities
Available-for-sale Securities Including Securities Pledged [Line Items]
Securities pledged, Amortized Cost	749	867
Securities pledged, Gross Unrealized Capital Gains	85	45
Securities pledged, Gross Unrealized Capital Losses	6	30
Embedded Derivatives	0	0
Securities pledged, Gross Unrealized Capital Losses	828	882
OTTI	$ 0	$ 0