INVESTMENT OPERATIONS - Schedule of Available-for-Sale Credit Losses on Fixed Maturities Held by the Company for Which a Portion of Other-than-Temporary Impairments were Recognized in Other Comprehensive Income (Loss) (Details) - Fixed maturities - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 2,783	$ 964	$ 12,685	$ 22,761
Additions for newly impaired securities	266	1,721	266	4,777
Additions for previously impaired securities	6	1,521	2,791	2,046
Reductions for previously impaired securities due to a change in expected cash flows	(37)	(4)	(12,724)	(22,763)
Reductions for previously impaired securities that were sold in the current period	(600)	0	(600)	(2,619)
Ending balance	$ 2,418	$ 4,202	$ 2,418	$ 4,202