INVESTMENT OPERATIONS - Schedule of Other-than-Temporary Impairments of Investments (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								11 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Investment [Line Items]
Other-than-temporary impairments										$ (28,659)	$ (3,962)	$ (32,075)
Non-credit impairment losses recorded in other comprehensive income										1,666	(7,780)	14,327
Net impairment losses recognized in earnings		$ (853)	$ (273)	$ (2,785)	$ (7,831)	$ (10,856)	$ (3,308)	$ (967)	$ (2,617)	(26,993)	(11,742)	(17,748)
Predecessor
Investment [Line Items]
Other-than-temporary impairments	$ (636)
Non-credit impairment losses recorded in other comprehensive income	155
Net impairment losses recognized in earnings	(481)
Fixed maturities
Investment [Line Items]
Other-than-temporary impairments										(28,659)	(1,332)	(32,075)
Non-credit impairment losses recorded in other comprehensive income										1,666	(7,780)	14,327
Net impairment losses recognized in earnings										(26,993)	(9,112)	(17,748)
Fixed maturities | Predecessor
Investment [Line Items]
Other-than-temporary impairments	(636)
Non-credit impairment losses recorded in other comprehensive income	155
Net impairment losses recognized in earnings	(481)
Equity securities
Investment [Line Items]
Other-than-temporary impairments										0	(2,630)	0
Non-credit impairment losses recorded in other comprehensive income										0	0	0
Net impairment losses recognized in earnings										$ 0	$ (2,630)	$ 0
Equity securities | Predecessor
Investment [Line Items]
Other-than-temporary impairments	0
Non-credit impairment losses recorded in other comprehensive income	0
Net impairment losses recognized in earnings	$ 0