INVESTMENTS - (Net Realized Gains (Losses) by Major Investment Category (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Total gross realized gains	$ 2,797	$ 11,758	$ 7,472
Total gross realized losses	(6,941)	(3,210)	(4,427)
Net realized gains on investments	(4,144)	8,548	3,045
Debt Securities [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Total gross realized gains	423	1,814	3,208
Total gross realized losses	(3,990)	(1,671)	(1,614)
Equity Securities [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Total gross realized gains	2,374	9,944	4,264
Total gross realized losses	$ (2,951)	$ (1,539)	$ (2,813)