Fair Value Measurements - Fair Value Measurement (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets:
Derivatives	$ 178	$ 224
Assets held in separate accounts	79,953	78,713
Liabilities:
Derivatives	250	285
U.S. Treasuries
Assets:
Fixed maturities, including securities pledged	749	691
US Treasury and Government
Assets:
Fixed maturities, including securities pledged	20	19
State, municipalities and political subdivisions
Assets:
Fixed maturities, including securities pledged	818	815
U.S. corporate public securities
Assets:
Fixed maturities, including securities pledged	8,633	8,031
U.S. corporate private securities
Assets:
Fixed maturities, including securities pledged	4,207	4,066
Foreign corporate public securities and foreign governments
Assets:
Fixed maturities, including securities pledged	2,860	2,679
Foreign corporate private securities
Assets:
Fixed maturities, including securities pledged	3,358	3,375
Residential mortgage-backed
Assets:
Fixed maturities, including securities pledged	4,301	3,810
Commercial mortgage-backed
Assets:
Fixed maturities, including securities pledged	2,959	2,500
Other asset-backed securities
Assets:
Fixed maturities, including securities pledged	1,503	1,474
Assets measured on recurring basis
Assets:
Fixed maturities, including securities pledged	29,408	27,460
Cash and cash equivalents, short-term investments and short-term investments under securities loan agreement	686	1,429
Assets held in separate accounts	79,953	78,713
Total assets, fair value	$ 110,444	$ 107,906
Percentage of Level to total assets	100.00%	100.00%
Liabilities:
Total liabilities, fair value	$ 384	$ 341
Assets measured on recurring basis | FIA
Liabilities:
Product guarantees	9	11
Assets measured on recurring basis | Stabilizer and MCGs
Liabilities:
Product guarantees	125	22
Assets measured on recurring basis | Interest rate contracts
Assets:
Derivatives	151	210
Liabilities:
Derivatives	237	261
Assets measured on recurring basis | Foreign exchange contracts
Assets:
Derivatives	24	10
Liabilities:
Derivatives	8	19
Assets measured on recurring basis | Equity contract
Assets:
Derivatives	3	4
Liabilities:
Derivatives	3	3
Assets measured on recurring basis | Embedded derivative on reinsurance
Liabilities:
Embedded derivative on reinsurance	0	23
Assets measured on recurring basis | Credit contracts
Liabilities:
Derivatives	2	2
Assets measured on recurring basis | U.S. Treasuries
Assets:
Fixed maturities, including securities pledged	749	691
Assets measured on recurring basis | US Treasury and Government
Assets:
Fixed maturities, including securities pledged	20	19
Assets measured on recurring basis | State, municipalities and political subdivisions
Assets:
Fixed maturities, including securities pledged	818	815
Assets measured on recurring basis | U.S. corporate public securities
Assets:
Fixed maturities, including securities pledged	8,633	8,031
Assets measured on recurring basis | U.S. corporate private securities
Assets:
Fixed maturities, including securities pledged	4,207	4,066
Assets measured on recurring basis | Foreign corporate public securities and foreign governments
Assets:
Fixed maturities, including securities pledged	2,860	2,679
Assets measured on recurring basis | Foreign corporate private securities
Assets:
Fixed maturities, including securities pledged	3,358	3,375
Assets measured on recurring basis | Residential mortgage-backed
Assets:
Fixed maturities, including securities pledged	4,301	3,810
Assets measured on recurring basis | Commercial mortgage-backed
Assets:
Fixed maturities, including securities pledged	2,959	2,500
Assets measured on recurring basis | Other asset-backed securities
Assets:
Fixed maturities, including securities pledged	1,503	1,474
Assets measured on recurring basis | Equity securities
Assets:
Equity securities	219	80
Assets measured on recurring basis | Level 1
Assets:
Fixed maturities, including securities pledged	571	536
Cash and cash equivalents, short-term investments and short-term investments under securities loan agreement	686	1,429
Assets held in separate accounts	73,390	72,448
Total assets, fair value	$ 74,773	$ 74,431
Percentage of Level to total assets	67.00%	69.00%
Liabilities:
Total liabilities, fair value	$ 0	$ 0
Assets measured on recurring basis | Level 1 | FIA
Liabilities:
Product guarantees	0	0
Assets measured on recurring basis | Level 1 | Stabilizer and MCGs
Liabilities:
Product guarantees	0	0
Assets measured on recurring basis | Level 1 | Interest rate contracts
Assets:
Derivatives	5	1
Liabilities:
Derivatives	0	0
Assets measured on recurring basis | Level 1 | Foreign exchange contracts
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Assets measured on recurring basis | Level 1 | Equity contract
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Assets measured on recurring basis | Level 1 | Embedded derivative on reinsurance
Liabilities:
Embedded derivative on reinsurance	0	0
Assets measured on recurring basis | Level 1 | Credit contracts
Liabilities:
Derivatives	0	0
Assets measured on recurring basis | Level 1 | U.S. Treasuries
Assets:
Fixed maturities, including securities pledged	571	536
Assets measured on recurring basis | Level 1 | US Treasury and Government
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 1 | State, municipalities and political subdivisions
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 1 | U.S. corporate public securities
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 1 | U.S. corporate private securities
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 1 | Foreign corporate public securities and foreign governments
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 1 | Foreign corporate private securities
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 1 | Residential mortgage-backed
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 1 | Commercial mortgage-backed
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 1 | Other asset-backed securities
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 1 | Equity securities
Assets:
Equity securities	121	17
Assets measured on recurring basis | Level 2
Assets:
Fixed maturities, including securities pledged	27,223	25,621
Cash and cash equivalents, short-term investments and short-term investments under securities loan agreement	0	0
Assets held in separate accounts	6,356	6,150
Total assets, fair value	$ 33,752	$ 31,994
Percentage of Level to total assets	31.00%	30.00%
Liabilities:
Total liabilities, fair value	$ 250	$ 308
Assets measured on recurring basis | Level 2 | FIA
Liabilities:
Product guarantees	0	0
Assets measured on recurring basis | Level 2 | Stabilizer and MCGs
Liabilities:
Product guarantees	0	0
Assets measured on recurring basis | Level 2 | Interest rate contracts
Assets:
Derivatives	146	209
Liabilities:
Derivatives	237	261
Assets measured on recurring basis | Level 2 | Foreign exchange contracts
Assets:
Derivatives	24	10
Liabilities:
Derivatives	8	19
Assets measured on recurring basis | Level 2 | Equity contract
Assets:
Derivatives	3	4
Liabilities:
Derivatives	3	3
Assets measured on recurring basis | Level 2 | Embedded derivative on reinsurance
Liabilities:
Embedded derivative on reinsurance	0	23
Assets measured on recurring basis | Level 2 | Credit contracts
Liabilities:
Derivatives	2	2
Assets measured on recurring basis | Level 2 | U.S. Treasuries
Assets:
Fixed maturities, including securities pledged	178	155
Assets measured on recurring basis | Level 2 | US Treasury and Government
Assets:
Fixed maturities, including securities pledged	20	19
Assets measured on recurring basis | Level 2 | State, municipalities and political subdivisions
Assets:
Fixed maturities, including securities pledged	818	815
Assets measured on recurring basis | Level 2 | U.S. corporate public securities
Assets:
Fixed maturities, including securities pledged	8,557	7,984
Assets measured on recurring basis | Level 2 | U.S. corporate private securities
Assets:
Fixed maturities, including securities pledged	3,028	3,064
Assets measured on recurring basis | Level 2 | Foreign corporate public securities and foreign governments
Assets:
Fixed maturities, including securities pledged	2,860	2,679
Assets measured on recurring basis | Level 2 | Foreign corporate private securities
Assets:
Fixed maturities, including securities pledged	3,071	3,185
Assets measured on recurring basis | Level 2 | Residential mortgage-backed
Assets:
Fixed maturities, including securities pledged	4,276	3,794
Assets measured on recurring basis | Level 2 | Commercial mortgage-backed
Assets:
Fixed maturities, including securities pledged	2,955	2,500
Assets measured on recurring basis | Level 2 | Other asset-backed securities
Assets:
Fixed maturities, including securities pledged	1,460	1,426
Assets measured on recurring basis | Level 2 | Equity securities
Assets:
Equity securities	0	0
Assets measured on recurring basis | Level 3
Assets:
Fixed maturities, including securities pledged	1,614	1,303
Cash and cash equivalents, short-term investments and short-term investments under securities loan agreement	0	0
Assets held in separate accounts	207	115
Total assets, fair value	$ 1,919	$ 1,481
Percentage of Level to total assets	2.00%	1.00%
Liabilities:
Total liabilities, fair value	$ 134	$ 33
Assets measured on recurring basis | Level 3 | FIA
Liabilities:
Product guarantees	9	11
Assets measured on recurring basis | Level 3 | Stabilizer and MCGs
Liabilities:
Product guarantees	125	22
Assets measured on recurring basis | Level 3 | Interest rate contracts
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Assets measured on recurring basis | Level 3 | Foreign exchange contracts
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Assets measured on recurring basis | Level 3 | Equity contract
Assets:
Derivatives	0	0
Liabilities:
Derivatives	0	0
Assets measured on recurring basis | Level 3 | Embedded derivative on reinsurance
Liabilities:
Embedded derivative on reinsurance	0	0
Assets measured on recurring basis | Level 3 | Credit contracts
Liabilities:
Derivatives	0	0
Assets measured on recurring basis | Level 3 | U.S. Treasuries
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 3 | US Treasury and Government
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 3 | State, municipalities and political subdivisions
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 3 | U.S. corporate public securities
Assets:
Fixed maturities, including securities pledged	76	47
Assets measured on recurring basis | Level 3 | U.S. corporate private securities
Assets:
Fixed maturities, including securities pledged	1,179	1,002
Assets measured on recurring basis | Level 3 | Foreign corporate public securities and foreign governments
Assets:
Fixed maturities, including securities pledged	0	0
Assets measured on recurring basis | Level 3 | Foreign corporate private securities
Assets:
Fixed maturities, including securities pledged	287	190
Assets measured on recurring basis | Level 3 | Residential mortgage-backed
Assets:
Fixed maturities, including securities pledged	25	16
Assets measured on recurring basis | Level 3 | Commercial mortgage-backed
Assets:
Fixed maturities, including securities pledged	4	0
Assets measured on recurring basis | Level 3 | Other asset-backed securities
Assets:
Fixed maturities, including securities pledged	43	48
Assets measured on recurring basis | Level 3 | Equity securities
Assets:
Equity securities	$ 98	$ 63