Investments - Fixed Maturities and Equity Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Jun. 30, 2020
Available-for-sale Securities Including Securities Pledged [Line Items]
Securities pledged, amortized costs	$ 749	$ 556
U.S. Treasuries
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	565	537
Fixed maturities, Gross Unrealized Capital Gains	129	213
Fixed maturities, Gross Unrealized Capital Losses	3	0
Embedded Derivatives	0	0
Fair Value	691	750
OTTI	0	0
US Treasury and Government
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	19	18
Fixed maturities, Gross Unrealized Capital Gains	0	1
Fixed maturities, Gross Unrealized Capital Losses	0	0
Embedded Derivatives	0	0
Fair Value	19	19
OTTI	0	0
State, municipalities and political subdivisions
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	747	734
Fixed maturities, Gross Unrealized Capital Gains	68	106
Fixed maturities, Gross Unrealized Capital Losses	0	0
Embedded Derivatives	0	0
Fair Value	815	840
OTTI	0	0
U.S. corporate public securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	7,103	6,941
Fixed maturities, Gross Unrealized Capital Gains	941	1,227
Fixed maturities, Gross Unrealized Capital Losses	13	38
Embedded Derivatives	0	0
Fair Value	8,031	8,130
OTTI	0	0
U.S. corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	3,776	3,774
Fixed maturities, Gross Unrealized Capital Gains	306	458
Fixed maturities, Gross Unrealized Capital Losses	16	31
Embedded Derivatives	0	0
Fair Value	4,066	4,201
OTTI	0	0
Foreign corporate public securities and foreign governments
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	2,417	2,412
Fixed maturities, Gross Unrealized Capital Gains	265	311
Fixed maturities, Gross Unrealized Capital Losses	3	11
Embedded Derivatives	0	0
Fair Value	2,679	2,712
OTTI	0	0
Foreign corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	3,171	3,078
Fixed maturities, Gross Unrealized Capital Gains	205	224
Fixed maturities, Gross Unrealized Capital Losses	1	29
Embedded Derivatives	0	0
Fair Value	3,375	3,272
OTTI	0	1
Residential mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	3,685	4,320
Fixed maturities, Gross Unrealized Capital Gains	125	188
Fixed maturities, Gross Unrealized Capital Losses	11	36
Embedded Derivatives	11	15
Fair Value	3,810	4,486
OTTI	2	1
Commercial mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	2,381	2,650
Fixed maturities, Gross Unrealized Capital Gains	122	178
Fixed maturities, Gross Unrealized Capital Losses	3	116
Embedded Derivatives	0	0
Fair Value	2,500	2,712
OTTI	0	0
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	1,472	1,493
Fixed maturities, Gross Unrealized Capital Gains	15	18
Fixed maturities, Gross Unrealized Capital Losses	13	38
Embedded Derivatives	0	0
Fair Value	1,474	1,470
OTTI	1	3
Embedded derivatives - fixed maturities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost	25,336	25,957
Fixed maturities, Gross Unrealized Capital Gains	2,176	2,924
Fixed maturities, Gross Unrealized Capital Losses	63	299
Embedded Derivatives	11	15
Fair Value	27,460	28,592
OTTI	3	5
Total fixed maturities, less securities pledged, Amortized Cost	24,587	25,401
Total fixed maturities, less securities pledged, Gross Unrealized Capital Gains	2,091	2,826
Total fixed maturities, less securities pledged, Gross Unrealized Capital Losses	57	293
Total fixed maturities, less securities pledged, Fair Value	26,632	27,944
Impaired available-for-sale securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Marketable Securities, Unrealized Gain (Loss)	137
Collateral Pledged
Available-for-sale Securities Including Securities Pledged [Line Items]
Securities pledged	828	648
Collateral Pledged | Embedded derivatives - fixed maturities
Available-for-sale Securities Including Securities Pledged [Line Items]
Embedded Derivatives	0	0
OTTI	0	0
Securities pledged, amortized costs	749	556
Securities pledged, Gross Unrealized Capital Gains	85	98
Securities pledged, Gross Unrealized Capital Losses	6	6
Securities pledged	$ 828	$ 648