INVESTMENT OPERATIONS - Summary of Change in Unrealized Gains (Losses), Net of Income Tax, on Fixed Maturity and Equity Securities, Classified as Available-for-Sale (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fixed maturities
Investment Holdings [Line Items]
Change in unrealized gains (losses), net of income tax	$ 1,541,352	$ (585,527)	$ 3,099,183	$ (1,505,298)