INVESTMENTS - AVAILABLE FOR SALE SECURITIES (Details) - USD ($)	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 40,542,000,000
Fair Value	39,754,000,000		$ 36,358,000,000
Amortized Cost		$ 40,542,000,000	34,988,000,000
Gross Unrealized Gains		555,000,000	1,774,000,000
Gross Unrealized Losses		1,343,000,000	247,000,000
Fair Value		39,754,000,000	36,515,000,000
OTTI in AOCI		$ 2,000,000	2,000,000
Amortized Cost
Due in one year or less	1,908,000,000
Due in years two through five	7,755,000,000
Due in years six through ten	12,941,000,000
Due after ten years	16,653,000,000
Subtotal	39,257,000,000
Fair Value
Due in one year or less	1,915,000,000
Due in years two through five	7,816,000,000
Due in years six through ten	12,719,000,000
Due after ten years	15,992,000,000
Subtotal	38,442,000,000
Total	39,754,000,000
Corporate
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	24,796,000,000
Gross Unrealized Gains	397,000,000
Gross Unrealized Losses	591,000,000
Fair Value	24,602,000,000
Amortized Cost			20,596,000,000
Gross Unrealized Gains			942,000,000
Gross Unrealized Losses			56,000,000
Fair Value			21,482,000,000
OTTI in AOCI	0		0
U.S. Treasury, government and agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	13,621,000,000
Gross Unrealized Gains	58,000,000
Gross Unrealized Losses	728,000,000
Fair Value	12,951,000,000
Amortized Cost			12,644,000,000
Gross Unrealized Gains			676,000,000
Gross Unrealized Losses			185,000,000
Fair Value			13,135,000,000
OTTI in AOCI	0		0
State and Political Sub- divisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	409,000,000
Gross Unrealized Gains	43,000,000
Gross Unrealized Losses	1,000,000
Fair Value	451,000,000
Amortized Cost			414,000,000
Gross Unrealized Gains			67,000,000
Gross Unrealized Losses			0
Fair Value			481,000,000
OTTI in AOCI	0		0
Foreign governments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	431,000,000
Gross Unrealized Gains	17,000,000
Gross Unrealized Losses	10,000,000
Fair Value	438,000,000
Amortized Cost			387,000,000
Gross Unrealized Gains			27,000,000
Gross Unrealized Losses			5,000,000
Fair Value			409,000,000
OTTI in AOCI	0		0
Residential mortgage-backed
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	200,000,000
Gross Unrealized Gains	8,000,000
Gross Unrealized Losses	0
Fair Value	208,000,000
Amortized Cost			236,000,000
Gross Unrealized Gains			15,000,000
Gross Unrealized Losses			0
Fair Value			251,000,000
OTTI in AOCI	0		0
Amortized Cost
Without single maturity date	200,000,000
Fair Value
Without single maturity date	208,000,000
Asset- backed
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	613,000,000
Gross Unrealized Gains	1,000,000
Gross Unrealized Losses	6,000,000
Fair Value	608,000,000
Amortized Cost			93,000,000
Gross Unrealized Gains			3,000,000
Gross Unrealized Losses			0
Fair Value			96,000,000
OTTI in AOCI	2,000,000		2,000,000
Amortized Cost
Without single maturity date	613,000,000
Fair Value
Without single maturity date	608,000,000
Redeemable preferred stock
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	472,000,000
Gross Unrealized Gains	31,000,000
Gross Unrealized Losses	7,000,000
Fair Value	496,000,000
Amortized Cost			461,000,000
Gross Unrealized Gains			44,000,000
Gross Unrealized Losses			1,000,000
Fair Value			504,000,000
OTTI in AOCI	0		0
Amortized Cost
Without single maturity date	472,000,000
Fair Value
Without single maturity date	496,000,000
Total Fixed Maturities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	40,542,000,000		34,831,000,000
Amortized Cost	$ 40,542,000,000		$ 34,831,000,000