INVESTMENTS - Portfolio Analysis (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) security position	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Securities in unrealized loss positions
Other-than-temporary impairment (OTTI) losses	$ 217	$ 2,559	$ 95
Fixed maturities and short-term investments on deposit with either regulatory authorities or banks	59,200
Unrealized gains (losses) recognized on equity securities still held at end of period	$ (28,700)	$ 47,200
Debt securities
Securities in unrealized loss positions
Number of unrealized loss positions | position	777
Number of securities in unrealized loss positions for 12 months or longer | security	302