CERTAIN NONTRADITIONAL LONG-DURATION CONTRACTS - Account Balances and Deferred Sales Inducement Asset (Details) - USD ($) $ in Thousands	1 Months Ended	11 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Activity in the Company's deferred sales inducement asset
Deferred asset, beginning of period		$ 0	$ 22,497	$ 11,756
Amounts deferred		14,557	14,246	16,212
Amortization		(2,801)	(5,787)	(5,471)
Deferred asset, end of period	$ 0	11,756	30,956	22,497
Annuity account
Certain Nontraditional Long-duration Contracts
Account balances of variable annuities with guarantees invested in variable annuity separate accounts			13,804,510	13,157,068
Equity mutual funds | Annuity account
Certain Nontraditional Long-duration Contracts
Account balances of variable annuities with guarantees invested in variable annuity separate accounts			8,798,847	8,071,204
Fixed income mutual funds | Annuity account
Certain Nontraditional Long-duration Contracts
Account balances of variable annuities with guarantees invested in variable annuity separate accounts			$ 5,005,663	$ 5,085,864
Predecessor
Activity in the Company's deferred sales inducement asset
Deferred asset, beginning of period	155,150	$ 154,093
Amounts deferred	82
Amortization	(1,139)
Deferred asset, end of period	$ 154,093