Schedule I - Summary of Investments (Details) $ in Millions	Dec. 31, 2016 USD ($)
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	$ 25,796
Amount at which shown in the Consolidated Balance Sheet	26,815
Fixed Maturties [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	19,942
Fair value	20,961
Amount at which shown in the Consolidated Balance Sheet	20,961
United States government and government agencies and authorities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	658
Fair value	877
Amount at which shown in the Consolidated Balance Sheet	877
States, municipalities and political subdivisions [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,342
Fair value	1,435
Amount at which shown in the Consolidated Balance Sheet	1,435
Foreign governments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,998
Fair value	2,113
Amount at which shown in the Consolidated Balance Sheet	2,113
Public utilities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,919
Fair value	2,024
Amount at which shown in the Consolidated Balance Sheet	2,024
All other corporate bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	13,556
Fair value	14,018
Amount at which shown in the Consolidated Balance Sheet	14,018
Mortgage and other asset-backed [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	461
Fair value	486
Amount at which shown in the Consolidated Balance Sheet	486
Redeemable preferred stocks [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	8
Fair value	8
Amount at which shown in the Consolidated Balance Sheet	8
Equity securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	583
Fair value	583
Amount at which shown in the Consolidated Balance Sheet	583
Industrial, miscellaneous and all other [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	500
Fair value	503
Amount at which shown in the Consolidated Balance Sheet	503
Non-redeemable preferred stock [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	83
Fair value	80
Amount at which shown in the Consolidated Balance Sheet	80
Commercial mortgage loans on real estate [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,666
Amount at which shown in the Consolidated Balance Sheet	1,666
Policy loans [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,452
Amount at which shown in the Consolidated Balance Sheet	1,452
Other long-term investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,462
Amount at which shown in the Consolidated Balance Sheet	1,462
Short-term investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	691
Amount at which shown in the Consolidated Balance Sheet	$ 691