DERIVATIVE FINANCIAL INSTRUMENTS - Realized Investment Gains (Losses), Derivative Instruments (Details) $ in Thousands	1 Months Ended	11 Months Ended	12 Months Ended
	Jan. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) position	Dec. 31, 2014 USD ($)
Successor
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		$ 29,997	$ (40,288)
Successor | Cash flow hedges | Interest rate swaps
Notional amount and fair value of the entity's derivative financial instruments
Positions held | position			0
Successor | Derivatives not designated as hedging instruments
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		29,997	$ (40,288)
Successor | Derivatives not designated as hedging instruments | Interest rate swaps
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		0	0
Successor | Derivatives not designated as hedging instruments | Embedded derivative - GLWB
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		4,412	68,056
Successor | Derivatives not designated as hedging instruments | Embedded derivative - Modco reinsurance treaties
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		166,092	390
Successor | Derivatives not designated as hedging instruments | Other derivatives
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		91	(24)
Successor | Derivatives not designated as hedging instruments | Annuity account
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		(135,299)	(49,692)
Successor | Derivatives not designated as hedging instruments | Annuity account | Interest rate futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		(14,818)	(3,450)
Successor | Derivatives not designated as hedging instruments | Annuity account | Equity futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		(5,033)	(106,431)
Successor | Derivatives not designated as hedging instruments | Annuity account | Currency futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		7,169	33,836
Successor | Derivatives not designated as hedging instruments | Annuity account | Variance swaps
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		0	0
Successor | Derivatives not designated as hedging instruments | Annuity account | Equity options
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		(27,733)	(60,962)
Successor | Derivatives not designated as hedging instruments | Annuity account | Interest rate swaptions
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		(13,354)	(1,161)
Successor | Derivatives not designated as hedging instruments | Annuity account | Interest rate swaps
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		(85,942)	20,420
Successor | Derivatives not designated as hedging instruments | FIA
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		123	(4,097)
Successor | Derivatives not designated as hedging instruments | FIA | Equity futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		(355)	4,248
Successor | Derivatives not designated as hedging instruments | FIA | Equity options
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		1,211	8,149
Successor | Derivatives not designated as hedging instruments | FIA | Embedded derivative—FIA
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		(738)	(16,494)
Successor | Derivatives not designated as hedging instruments | FIA | Volatility futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		5	0
Successor | Derivatives not designated as hedging instruments | IUL
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		(1,010)	13,135
Successor | Derivatives not designated as hedging instruments | IUL | Equity futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		144	129
Successor | Derivatives not designated as hedging instruments | IUL | Equity options
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		(540)	3,477
Successor | Derivatives not designated as hedging instruments | IUL | Embedded derivative—IUL
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross		$ (614)	$ 9,529
Predecessor
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	$ (123,274)			$ (346,878)
Predecessor | Derivatives not designated as hedging instruments
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	(123,274)			(346,878)
Predecessor | Derivatives not designated as hedging instruments | Interest rate swaps
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	0			0
Predecessor | Derivatives not designated as hedging instruments | Embedded derivative - GLWB
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	(207,018)			(401,354)
Predecessor | Derivatives not designated as hedging instruments | Embedded derivative - Modco reinsurance treaties
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	(68,026)			(105,276)
Predecessor | Derivatives not designated as hedging instruments | Other derivatives
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	(37)			(323)
Predecessor | Derivatives not designated as hedging instruments | Annuity account
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	(53,581)			(235,300)
Predecessor | Derivatives not designated as hedging instruments | Annuity account | Interest rate futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	1,413			27,801
Predecessor | Derivatives not designated as hedging instruments | Annuity account | Equity futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	9,221			(26,104)
Predecessor | Derivatives not designated as hedging instruments | Annuity account | Currency futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	7,778			14,433
Predecessor | Derivatives not designated as hedging instruments | Annuity account | Variance swaps
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	0			(744)
Predecessor | Derivatives not designated as hedging instruments | Annuity account | Equity options
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	3,047			(41,216)
Predecessor | Derivatives not designated as hedging instruments | Annuity account | Interest rate swaptions
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	9,268			(22,280)
Predecessor | Derivatives not designated as hedging instruments | Annuity account | Interest rate swaps
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	122,710			214,164
Predecessor | Derivatives not designated as hedging instruments | FIA
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	(1,032)			(6,136)
Predecessor | Derivatives not designated as hedging instruments | FIA | Equity futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	(184)			870
Predecessor | Derivatives not designated as hedging instruments | FIA | Equity options
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	(2,617)			9,906
Predecessor | Derivatives not designated as hedging instruments | FIA | Embedded derivative—FIA
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	1,769			(16,932)
Predecessor | Derivatives not designated as hedging instruments | FIA | Volatility futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	0			20
Predecessor | Derivatives not designated as hedging instruments | IUL
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	(598)			157
Predecessor | Derivatives not designated as hedging instruments | IUL | Equity futures
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	3			15
Predecessor | Derivatives not designated as hedging instruments | IUL | Equity options
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	(115)			150
Predecessor | Derivatives not designated as hedging instruments | IUL | Embedded derivative—IUL
Realized investment gains (losses) - derivative instruments
Realized investment gains (losses) - derivatives, gross	$ (486)			$ (8)