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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	$ 12,498	$ 2	$ 24,868	$ 3,268
Additions for newly impaired securities	10,805	0	11,556	0
Additions for previously impaired securities	0	0	3,007	2
Reductions for previously impaired securities due to a change in expected cash flows	(12,498)	0	(21,332)	0
Reductions for previously impaired securities that were sold in the current period	0	(2)	(7,294)	(3,270)
Ending balance	$ 10,805	$ 0	$ 10,805	$ 0