Investments - Fixed Maturities and Equity Securities (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Available-for-sale Securities Including Securities Pledged [Line Items]
Securities pledged, amortized costs		$ 396	$ 749
U.S. Treasuries
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		542	565
Fixed maturities, Gross Unrealized Capital Gains		207	129
Fixed maturities, Gross Unrealized Capital Losses		0	3
Embedded Derivatives		0	0
Fair Value		749	691
OTTI		0	0
US Treasury and Government
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		18	19
Fixed maturities, Gross Unrealized Capital Gains		2	0
Fixed maturities, Gross Unrealized Capital Losses		0	0
Embedded Derivatives		0	0
Fair Value		20	19
OTTI		0	0
State, municipalities and political subdivisions
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		700	747
Fixed maturities, Gross Unrealized Capital Gains		118	68
Fixed maturities, Gross Unrealized Capital Losses		0	0
Embedded Derivatives		0	0
Fair Value		818	815
OTTI		0	0
U.S. corporate public securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		7,348	7,103
Fixed maturities, Gross Unrealized Capital Gains		1,317	941
Fixed maturities, Gross Unrealized Capital Losses		32	13
Embedded Derivatives		0	0
Fair Value		8,633	8,031
OTTI		0	0
U.S. corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		3,719	3,776
Fixed maturities, Gross Unrealized Capital Gains		519	306
Fixed maturities, Gross Unrealized Capital Losses		31	16
Embedded Derivatives		0	0
Fair Value		4,207	4,066
OTTI		0	0
Foreign corporate public securities and foreign governments
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		2,521	2,417
Fixed maturities, Gross Unrealized Capital Gains		348	265
Fixed maturities, Gross Unrealized Capital Losses		9	3
Embedded Derivatives		0	0
Fair Value		2,860	2,679
OTTI		0	0
Foreign corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		3,089	3,171
Fixed maturities, Gross Unrealized Capital Gains		300	205
Fixed maturities, Gross Unrealized Capital Losses		31	1
Embedded Derivatives		0	0
Fair Value		3,358	3,375
OTTI		0	0
Residential mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		4,134	3,685
Fixed maturities, Gross Unrealized Capital Gains		185	125
Fixed maturities, Gross Unrealized Capital Losses		29	11
Embedded Derivatives		13	11
Fair Value		4,301	3,810
OTTI		2	2
Commercial mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		2,825	2,381
Fixed maturities, Gross Unrealized Capital Gains		192	122
Fixed maturities, Gross Unrealized Capital Losses		57	3
Embedded Derivatives		0	0
Fair Value		2,959	2,500
OTTI		1	0
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		1,499	1,472
Fixed maturities, Gross Unrealized Capital Gains		25	15
Fixed maturities, Gross Unrealized Capital Losses		18	13
Embedded Derivatives		0	0
Fair Value		1,503	1,474
OTTI		3	1
Embedded derivatives - fixed maturities
Available-for-sale Securities Including Securities Pledged [Line Items]
Amortized Cost		26,395	25,336
Fixed maturities, Gross Unrealized Capital Gains		3,213	2,176
Fixed maturities, Gross Unrealized Capital Losses		207	63
Embedded Derivatives		13	11
Fair Value		29,408	27,460
OTTI		6	3
Total fixed maturities, less securities pledged, Amortized Cost		25,999	24,587
Total fixed maturities, less securities pledged, Gross Unrealized Capital Gains		3,130	2,091
Total fixed maturities, less securities pledged, Gross Unrealized Capital Losses		204	57
Total fixed maturities, less securities pledged, Fair Value		28,932	26,632
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		476	828
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		396	749
Securities pledged, Gross Unrealized Capital Gains		83	85
Securities pledged, Gross Unrealized Capital Losses		3	6
Securities pledged		$ 476	$ 828