INVESTMENTS - (Net Unrealized Gains (Losses) Still Held (Details) - Equity securities - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Investments [Line Items]
Net gains (losses) on equity securities: Realized	$ 4,555	$ 803	$ 591
Net gains (losses) on equity securities: Unrealized	(4,114)	4,116	(1,168)
Net gains (losses) on equity securities:	441	4,919	(577)
Less: Net realized and unrealized gains (losses) on securities sold	309	672	732
Net unrealized gains (losses) still held as of the end-of-period	$ 132	$ 4,247	$ (1,309)