MONY CLOSED BLOCK OF BUSINESS - Summary of Financial Information for the Closed Block (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Closed block liabilities
Future policy benefits, policyholders’ account balances and other policyholder liabilities	$ 5,699,118	$ 5,791,867
Policyholder dividend obligation	0	160,712	$ 136,004	$ 31,932
Other liabilities	42,640	30,764
Total closed block liabilities	5,741,758	5,983,343
Closed block assets
Fixed maturities, available-for-sale, at fair value	4,339,342	4,669,856
Mortgage loans on real estate	76,608	108,934
Policy loans	679,760	700,769
Cash	72,868	31,182
Other assets	144,077	122,637
Total closed block assets	5,312,655	5,633,378
Excess of reported closed block liabilities over closed block assets	429,103	349,965
Portion of above representing accumulated other comprehensive income:
Net unrealized investment gains (losses) net of policyholder dividend obligation: $(149,219) and $(13,429); and net of income tax: $57,054 and $2,820	(96,749)	0
Future earnings to be recognized from closed block assets and closed block liabilities	332,354	349,965
Policyholder dividend obligations	(149,219)	(13,429)
Deferred income tax expense (benefit)	$ 57,054	$ 2,820