Schedule I. Summary of Investments (Details) $ in Millions	Dec. 31, 2019 USD ($)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	$ 31,017
Fair Value	33,582
Amount Shown on Consolidated Balance Sheets	33,414
U.S. Treasuries
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	565
Fair Value	691
Amount Shown on Consolidated Balance Sheets	691
U.S. Government agencies and authorities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	19
Fair Value	19
Amount Shown on Consolidated Balance Sheets	19
State, municipalities and political subdivisions
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	747
Fair Value	815
Amount Shown on Consolidated Balance Sheets	815
U.S. corporate public securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	7,103
Fair Value	8,031
Amount Shown on Consolidated Balance Sheets	8,031
U.S. corporate private securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	3,776
Fair Value	4,066
Amount Shown on Consolidated Balance Sheets	4,066
Foreign corporate public securities and foreign governments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	2,417
Fair Value	2,679
Amount Shown on Consolidated Balance Sheets	2,679
Foreign corporate private securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	3,171
Fair Value	3,375
Amount Shown on Consolidated Balance Sheets	3,375
Residential mortgage-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	3,685
Fair Value	3,810
Amount Shown on Consolidated Balance Sheets	3,810
Commercial mortgage-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	2,381
Fair Value	2,500
Amount Shown on Consolidated Balance Sheets	2,500
Other asset-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	1,472
Fair Value	1,474
Amount Shown on Consolidated Balance Sheets	1,474
Total fixed maturities, including securities pledged
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	25,336
Fair Value	27,460
Amount Shown on Consolidated Balance Sheets	27,460
Equity securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	0
Fair Value	0
Amount Shown on Consolidated Balance Sheets	80
Mortgage loans on real estate
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	4,664
Fair Value	4,912
Amount Shown on Consolidated Balance Sheets	4,664
Policy loans
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	205
Fair Value	205
Amount Shown on Consolidated Balance Sheets	205
Limited partnerships/corporations
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	738
Fair Value	738
Amount Shown on Consolidated Balance Sheets	738
Derivatives
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	31
Fair Value	224
Amount Shown on Consolidated Balance Sheets	224
Other investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	43
Fair Value	43
Amount Shown on Consolidated Balance Sheets	$ 43