Schedule I Summary of Investments - Other Than Investments in Affiliates (Details) $ in Millions	Dec. 31, 2020 USD ($)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	$ 53,142
Amount at which shown on Balance Sheet	56,532
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	4,872
Fair Value	5,214
Amount at which shown on Balance Sheet	5,214
States, municipalities and political subdivisions
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	8,564
Fair Value	9,503
Amount at which shown on Balance Sheet	9,503
Foreign government/government agencies
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	842
Fair Value	919
Amount at which shown on Balance Sheet	919
Public utilities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	1,999
Fair Value	2,249
Amount at which shown on Balance Sheet	2,249
All other corporate bonds
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	16,402
Fair Value	18,024
Amount at which shown on Balance Sheet	18,024
Industrial, miscellaneous and all other
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	932
Fair Value	932
Amount at which shown on Balance Sheet	932
Non-redeemable preferred stocks
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	506
Fair Value	506
Amount at which shown on Balance Sheet	506
Equity securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	1,438
Fair Value	1,438
Amount at which shown on Balance Sheet	1,438
Mortgage loans [1]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	4,531
Fair Value	4,792
Amount at which shown on Balance Sheet	4,493
Futures, options and miscellaneous
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	247
Fair Value	201
Amount at which shown on Balance Sheet	201
Short-term investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	3,283
Fair Value	3,283
Amount at which shown on Balance Sheet	3,283
Investments in partnerships and trusts
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	2,082
Amount at which shown on Balance Sheet	2,082
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	8,882
Fair Value	9,126
Amount at which shown on Balance Sheet	9,126
Total fixed maturities, available-for-sale
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Cost	41,561
Fair Value	45,035
Amount at which shown on Balance Sheet	$ 45,035