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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 27,215	$ 2,235	$ 24,868	$ 3,268
Additions for newly impaired securities	0	0	751	0
Additions for previously impaired securities	660	2	3,007	2
Reductions for previously impaired securities due to a change in expected cash flows	(8,202)	0	(8,834)	0
Reductions for previously impaired securities that were sold in the current period	(7,175)	(2,235)	(7,294)	(3,268)
Ending balance	$ 12,498	$ 2	$ 12,498	$ 2