INVESTMENTS - GROSS UNREALIZED LOSSES (Details) $ in Millions	Mar. 31, 2018 USD ($) security	Dec. 31, 2017 USD ($) security
Investments, Debt and Equity Securities [Abstract]
Number of fixed maturities in an unrealized loss position greater than 12 months | security	1,188	620
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	$ 11,207	$ 4,315
Less Than 12 Months, Gross Unrealized Losses	339	23
Greater than 12 Months, Fair Value	4,019	4,255
Greater Than 12 Months, Gross Unrealized Losses	404	224
Total, Fair Value	15,226	8,570
Total, Gross Unrealized Losses	743	247
Public corporate
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	6,461	1,384
Less Than 12 Months, Gross Unrealized Losses	209	9
Greater than 12 Months, Fair Value	443	548
Greater Than 12 Months, Gross Unrealized Losses	27	16
Total, Fair Value	6,904	1,932
Total, Gross Unrealized Losses	236	25
Private corporate
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	2,299	718
Less Than 12 Months, Gross Unrealized Losses	58	8
Greater than 12 Months, Fair Value	634	615
Greater Than 12 Months, Gross Unrealized Losses	42	23
Total, Fair Value	2,933	1,333
Total, Gross Unrealized Losses	100	31
U.S. Treasury, government and agency
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	2,172	2,150
Less Than 12 Months, Gross Unrealized Losses	65	6
Greater than 12 Months, Fair Value	2,859	3,005
Greater Than 12 Months, Gross Unrealized Losses	325	179
Total, Fair Value	5,031	5,155
Total, Gross Unrealized Losses	390	185
State and Political Sub- divisions
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	19	20
Less Than 12 Months, Gross Unrealized Losses	1	0
Greater than 12 Months, Fair Value	0	0
Greater Than 12 Months, Gross Unrealized Losses	0	0
Total, Fair Value	19	20
Total, Gross Unrealized Losses	1	0
Foreign governments
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	57	11
Less Than 12 Months, Gross Unrealized Losses	1	0
Greater than 12 Months, Fair Value	70	73
Greater Than 12 Months, Gross Unrealized Losses	8	5
Total, Fair Value	127	84
Total, Gross Unrealized Losses	9	5
Residential mortgage-backed
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	17	18
Less Than 12 Months, Gross Unrealized Losses	0	0
Greater than 12 Months, Fair Value	0	0
Greater Than 12 Months, Gross Unrealized Losses	0	0
Total, Fair Value	17	18
Total, Gross Unrealized Losses	0	0
Asset- backed
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	70	7
Less Than 12 Months, Gross Unrealized Losses	3	0
Greater than 12 Months, Fair Value	1	2
Greater Than 12 Months, Gross Unrealized Losses	0	0
Total, Fair Value	71	9
Total, Gross Unrealized Losses	3	0
Redeemable preferred stock
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	112	7
Less Than 12 Months, Gross Unrealized Losses	2	0
Greater than 12 Months, Fair Value	12	12
Greater Than 12 Months, Gross Unrealized Losses	2	1
Total, Fair Value	124	19
Total, Gross Unrealized Losses	$ 4	$ 1