SCHEDULE I - SUMMARY OF INVESTMENTS OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) $ in Millions	Dec. 31, 2017 USD ($)
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	$ 32,873
Amount at which shown in the Balance Sheet	34,438
United States government, government agencies and authorities
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	768
Fair value	804
Amount at which shown in the Balance Sheet	804
States, municipalities and political subdivisions
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	2,001
Fair value	2,273
Amount at which shown in the Balance Sheet	2,273
Foreign government
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	279
Fair value	299
Amount at which shown in the Balance Sheet	299
Public utilities
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	3,456
Fair value	3,780
Amount at which shown in the Balance Sheet	3,780
All other corporate bonds
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	14,806
Fair value	15,356
Amount at which shown in the Balance Sheet	15,356
Asset-backed securities
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	383
Fair value	385
Amount at which shown in the Balance Sheet	385
Residential mortgage-backed securities
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	205
Fair value	253
Amount at which shown in the Balance Sheet	253
CMBS
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	93
Fair value	97
Amount at which shown in the Balance Sheet	97
Redeemable preferred stock
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	13
Fair value	14
Amount at which shown in the Balance Sheet	14
Fixed income securities
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	22,004
Fair value	23,261
Amount at which shown in the Balance Sheet	23,261
Public utilities
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	27
Fair value	31
Amount at which shown in the Balance Sheet	31
Banks, trusts and insurance companies
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	165
Fair value	215
Amount at which shown in the Balance Sheet	215
Industrial, miscellaneous and all other
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	1,087
Fair value	1,341
Amount at which shown in the Balance Sheet	1,341
Nonredeemable preferred stocks
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	27
Fair value	27
Amount at which shown in the Balance Sheet	27
Equity securities
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	1,306
Fair value	1,614
Amount at which shown in the Balance Sheet	1,614
Mortgage loans on real estate
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	3,876
Fair value	4,052
Amount at which shown in the Balance Sheet	3,876
Real Estate Acquired in Satisfaction of Debt
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	0
Amount at which shown in the Balance Sheet	0
Real estate investment
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	157
Amount at which shown in the Balance Sheet	157
Policy loans
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	561
Amount at which shown in the Balance Sheet	561
Derivative instruments
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	115
Fair value	115
Amount at which shown in the Balance Sheet	115
Limited partnership interests
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	3,147
Amount at which shown in the Balance Sheet	3,147
Other long-term investments
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	982
Amount at which shown in the Balance Sheet	982
Short-term investments
Summary of Investments Other Than Investments in Related Parties
Cost/ amortized cost	725
Fair value	725
Amount at which shown in the Balance Sheet	$ 725