INVESTMENTS - Gross Unrealized Losses (Details) $ in Millions	Mar. 31, 2019 USD ($) security	Dec. 31, 2018 USD ($) security
Investments, Debt and Equity Securities [Abstract]
Number of fixed maturities in an unrealized loss position greater than 12 months | security	674	1,471
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	$ 976	$ 11,832
Less Than 12 Months, Gross Unrealized Losses	8	400
Greater than 12 Months, Fair Value	8,901	9,460
Greater Than 12 Months, Gross Unrealized Losses	427	795
Total, Fair Value	9,877	21,292
Total, Gross Unrealized Losses	435	1,195
Corporate
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	653	8,369
Less Than 12 Months, Gross Unrealized Losses	6	306
Greater than 12 Months, Fair Value	5,387	6,161
Greater Than 12 Months, Gross Unrealized Losses	202	393
Total, Fair Value	6,040	14,530
Total, Gross Unrealized Losses	208	699
U.S. Treasury, government and agency
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	0	2,636
Less Than 12 Months, Gross Unrealized Losses	0	68
Greater than 12 Months, Fair Value	3,163	3,154
Greater Than 12 Months, Gross Unrealized Losses	213	386
Total, Fair Value	3,163	5,790
Total, Gross Unrealized Losses	213	454
State and Political Sub-divisions
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value		0
Less Than 12 Months, Gross Unrealized Losses		0
Greater than 12 Months, Fair Value		19
Greater Than 12 Months, Gross Unrealized Losses		1
Total, Fair Value		19
Total, Gross Unrealized Losses		1
Foreign governments
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	0	109
Less Than 12 Months, Gross Unrealized Losses	0	3
Greater than 12 Months, Fair Value	67	76
Greater Than 12 Months, Gross Unrealized Losses	7	10
Total, Fair Value	67	185
Total, Gross Unrealized Losses	7	13
Residential mortgage-backed
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value		0
Less Than 12 Months, Gross Unrealized Losses		0
Greater than 12 Months, Fair Value		13
Greater Than 12 Months, Gross Unrealized Losses		0
Total, Fair Value		13
Total, Gross Unrealized Losses		0
Asset- backed
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	279	558
Less Than 12 Months, Gross Unrealized Losses	1	11
Greater than 12 Months, Fair Value	249	6
Greater Than 12 Months, Gross Unrealized Losses	3	0
Total, Fair Value	528	564
Total, Gross Unrealized Losses	4	11
Redeemable preferred stock
Available For Sale Securities Continuous Unrealized Loss Position [Line Items]
Less Than 12 Months, Fair Value	44	160
Less Than 12 Months, Gross Unrealized Losses	1	12
Greater than 12 Months, Fair Value	35	31
Greater Than 12 Months, Gross Unrealized Losses	2	5
Total, Fair Value	79	191
Total, Gross Unrealized Losses	$ 3	$ 17