MONY CLOSED BLOCK OF BUSINESS - Summary of Financial Information of the Policyholder Dividend Obligation (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Closed block liabilities
Future policy benefits, policyholders’ account balances and other policyholder liabilities	$ 5,728,327	$ 5,791,867
Policyholder dividend obligation	0	160,712	$ 123,449	$ 31,932
Other liabilities	25,595	30,764
Total closed block liabilities	5,753,922	5,983,343
Closed block assets
Fixed maturities, available-for-sale, at fair value	4,345,031	4,669,856
Mortgage loans on real estate	77,374	108,934
Policy loans	687,771	700,769
Cash	101,426	31,182
Other assets	130,468	122,637
Total closed block assets	5,342,070	5,633,378
Excess of reported closed block liabilities over closed block assets	411,852	349,965
Portion of above representing accumulated other comprehensive income:
Net unrealized investment gains (losses) net of policyholder dividend obligation: $(154,605) and $(13,429); and net of income tax: $52,196 and $2,820	(74,217)	0
Future earnings to be recognized from closed block assets and closed block liabilities	337,635	349,965
Net unrealized investment gains (losses) allocated to policyholder dividend obligation, net of deferred tax benefits	(154,605)	(13,429)
Net unrealized investment gains (losses), income tax	$ 52,196	$ 2,820