Schedule I Summary of Investments - Other than Investments in Related Parties (Details) $ in Millions	Dec. 31, 2018 USD ($)
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	$ 312,111
Fair Value	315,617
Amount at which shown in the Balance Sheet	315,125
Fixed maturity securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	237,195
Fair Value	240,806
Amount at which shown in the Balance Sheet	240,806
U.S. government and government sponsored entities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	5,835
Fair Value	5,925
Amount at which shown in the Balance Sheet	5,925
Obligations of states, municipalities and political subdivisions
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	15,421
Fair Value	16,001
Amount at which shown in the Balance Sheet	16,001
Non-U.S. government
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	14,421
Fair Value	14,570
Amount at which shown in the Balance Sheet	14,570
Public utilities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	17,431
Fair Value	17,628
Amount at which shown in the Balance Sheet	17,628
All other corporate and debt securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	114,676
Fair Value	114,743
Amount at which shown in the Balance Sheet	114,743
Mortgage-backed, asset-backed and collateralized
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	69,411
Fair Value	71,939
Amount at which shown in the Balance Sheet	71,939
Equity securities and mutual funds
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,253
Fair Value	1,253
Amount at which shown in the Balance Sheet	1,253
Common Stock
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,105
Fair Value	1,105
Amount at which shown in the Balance Sheet	1,105
Public utilities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1
Fair Value	1
Amount at which shown in the Balance Sheet	1
Banks, trust and insurance companies
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	784
Fair Value	784
Amount at which shown in the Balance Sheet	784
Industrial, miscellaneous and all other
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	320
Fair Value	320
Amount at which shown in the Balance Sheet	320
Preferred stock
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	13
Fair Value	13
Amount at which shown in the Balance Sheet	13
Mutual funds
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	135
Fair Value	135
Amount at which shown in the Balance Sheet	135
Mortgage and other loans receivable, net of allowance
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	43,135
Fair Value	43,627
Amount at which shown in the Balance Sheet	43,135
Other invested assets
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	19,938
Fair Value	19,341
Amount at which shown in the Balance Sheet	19,341
Short-term investments, at cost
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	9,674
Fair Value	9,674
Amount at which shown in the Balance Sheet	9,674
Derivative assets
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	916
Fair Value	916
Amount at which shown in the Balance Sheet	$ 916