MARKETABLE SECURITIES - Narrative (Details)	3 Months Ended
	Mar. 31, 2020 USD ($) Position security	Mar. 31, 2019 security	Dec. 31, 2019 USD ($)
Investments Debt And Equity Securities [Abstract]
Allowance for credit losses for available for sale debt securities	$ 0
Other than temporary impairment losses on debt securities related to credit losses			$ 0
Number of investment positions in an unrealized loss position | Position	66
Percentage of unrealized loss exceeds book value	20.00%
Number of securities other than agencies amount | security	0
Fair value of securities pledged as collateral	$ 300,214,000		$ 278,318,000
Number of securities sold | security	0	0