INVESTMENTS - Portfolio Analysis (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) security position	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Securities in unrealized loss positions
Other-than-temporary impairment (OTTI) losses	$ 0	$ 217,000	$ 2,559,000
Fixed maturities and short-term investments on deposit with either regulatory authorities or banks	69,600,000
Unrealized gains (losses) recognized on equity securities still held at end of period	$ 92,800,000	$ (28,700,000)	$ 47,200,000
Debt securities
Securities in unrealized loss positions
Number of unrealized loss positions | position	154
Number of securities in unrealized loss positions for 12 months or longer | security	65
12 months and greater	$ 900,000