INVESTMENT OPERATIONS - Schedule of Available-for-Sale Credit Losses on Fixed Maturities With Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Additions for securities for which allowance was not previously recorded	$ 30,288	$ 82,081
Ending Balance	82,081	82,081
Corporate securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning Balance	51,135	0
Additions for securities for which allowance was not previously recorded	11,307	62,442
Adjustments on previously recorded allowances due to change in expected cash flows	18,984	18,984
Reductions on previously recorded allowances due to disposal of security in the current period	0	0
Ending Balance	81,426	81,426
Other asset-backed securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning Balance	658	0
Additions for securities for which allowance was not previously recorded	0	658
Adjustments on previously recorded allowances due to change in expected cash flows	0	0
Reductions on previously recorded allowances due to disposal of security in the current period	(3)	(3)
Ending Balance	655	655
Fixed maturities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Beginning Balance	51,793	0
Additions for securities for which allowance was not previously recorded	11,307	63,100
Adjustments on previously recorded allowances due to change in expected cash flows	18,984	18,984
Reductions on previously recorded allowances due to disposal of security in the current period	(3)	(3)
Ending Balance	$ 82,081	$ 82,081