DERIVATIVE FINANCIAL INSTRUMENTS - Realized Investments Gains and Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	$ 15,337	$ 42,286	$ 92,899	$ (86,288)
Derivatives not designated as hedging instruments
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	15,337	42,286	92,899	(86,288)
Derivatives not designated as hedging instruments | Embedded derivative - Modco reinsurance treaties
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	(25,438)	(44,027)	(55,864)	(199,704)
Derivatives not designated as hedging instruments | Derivatives with PLC
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	19,833	7,583	22,179	14,852
Derivatives not designated as hedging instruments | Other derivatives
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	5,430	(1,622)	10,818	(3,011)
Derivatives not designated as hedging instruments | VA
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	(20,866)	72,002	155,060	117,229
Derivatives not designated as hedging instruments | VA | Interest rate futures
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	2,257	727	(3,565)	(16,575)
Derivatives not designated as hedging instruments | VA | Equity futures
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	(1,187)	5,220	131,912	37,517
Derivatives not designated as hedging instruments | VA | Currency futures
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	(9,536)	9,181	1,438	11,028
Derivatives not designated as hedging instruments | VA | Equity options
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	(41,584)	(3,957)	66,647	(97,354)
Derivatives not designated as hedging instruments | VA | Interest rate swaps
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	(57,657)	149,766	363,644	342,561
Derivatives not designated as hedging instruments | VA | Total return swaps
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	(31,465)	(1,950)	30,680	(50,522)
Derivatives not designated as hedging instruments | VA | Embedded derivative - GLWB
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	72,519	(86,635)	(332,202)	(189,624)
Derivatives not designated as hedging instruments | VA | Funds withheld derivative
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	45,787	(350)	(103,494)	80,198
Derivatives not designated as hedging instruments | FIA
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	14,425	1,412	(38,912)	(6,978)
Derivatives not designated as hedging instruments | FIA | Equity futures
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	518	962	(6,550)	964
Derivatives not designated as hedging instruments | FIA | Equity options
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	24,870	4,785	15,031	60,026
Derivatives not designated as hedging instruments | FIA | Funds withheld derivative
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	(2,804)	0	(9,586)	0
Derivatives not designated as hedging instruments | FIA | Embedded derivative - FIA
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	(8,642)	(4,335)	(38,065)	(67,968)
Derivatives not designated as hedging instruments | FIA | Other derivatives
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	483	0	258	0
Derivatives not designated as hedging instruments | IUL
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	21,953	6,938	(382)	(8,676)
Derivatives not designated as hedging instruments | IUL | Equity futures
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	(230)	91	(2,374)	347
Derivatives not designated as hedging instruments | IUL | Equity options
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	6,535	586	583	9,372
Derivatives not designated as hedging instruments | IUL | Embedded derivative - IUL
Notional amount and fair value of the entity's derivative financial instruments
Total realized gains (losses) - derivatives	$ 15,648	$ 6,261	$ 1,409	$ (18,395)