Schedule I Summary of Investments - Other Than Investments in Affiliates (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	$ 51,012
Amount at which shown on Balance Sheet	53,030
U.S. government and government agencies and authorities (guaranteed and sponsored)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	5,478
Fair Value	5,644
Amount at which shown on Balance Sheet	5,644
States, municipalities and political subdivisions
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	8,763
Fair Value	9,498
Amount at which shown on Balance Sheet	9,498
Foreign government/government agencies
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	1,057
Fair Value	1,123
Amount at which shown on Balance Sheet	1,123
Public utilities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	2,019
Fair Value	2,147
Amount at which shown on Balance Sheet	2,147
All other corporate bonds
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	14,416
Fair Value	15,249
Amount at which shown on Balance Sheet	15,249
All other mortgage-backed and asset-backed securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	8,345
Fair Value	8,487
Amount at which shown on Balance Sheet	8,487
Total fixed maturities, available-for-sale
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	40,078
Fair Value	42,148
Amount at which shown on Balance Sheet	42,148
Fixed maturities, at fair value using fair value option
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	11
Fair Value	11
Amount at which shown on Balance Sheet	11
Total fixed maturities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	40,089
Fair Value	42,159
Amount at which shown on Balance Sheet	42,159
Industrial, miscellaneous and all other
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	1,471
Fair Value	1,471
Amount at which shown on Balance Sheet	1,471
Non-redeemable preferred stocks
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	186
Fair Value	186
Amount at which shown on Balance Sheet	186
Equity securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	1,657
Fair Value	1,657
Amount at which shown on Balance Sheet	1,657
Mortgage loans
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	4,215
Fair Value	4,350
Amount at which shown on Balance Sheet	4,215
Futures, options and miscellaneous
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	376
Fair Value	320
Amount at which shown on Balance Sheet	320
Short-term investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	2,917
Fair Value	2,921
Amount at which shown on Balance Sheet	2,921
Investments in partnerships and trusts
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	1,758
Amount at which shown on Balance Sheet	$ 1,758