INVESTMENT OPERATIONS - Schedule of Gross Realized Gains (Losses) on Investments Available-for-Sale (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 2,750	$ 20,155	$ 49,189	$ 34,801
Gross realized losses:
Credit losses	(38,459)		(120,540)
Impairment losses		(10,818)		(14,658)
Other realized losses	$ (69)	$ (4,469)	$ (4,891)	$ (12,916)