INVESTMENTS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 144,401,000	$ 279,848,000
Unrealized Gains	47,000	651,000
Unrealized Losses	(461,000)	(37,000)
Fair Value	143,987,000	280,462,000
Impairment loss	0	0
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		35,543,000
Unrealized Gains		21,000
Unrealized Losses		(5,000)
Fair Value		35,559,000
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	104,261,000	191,977,000
Unrealized Gains	47,000	608,000
Unrealized Losses	(242,000)	(12,000)
Fair Value	104,066,000	192,573,000
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	40,140,000	52,328,000
Unrealized Gains	0	22,000
Unrealized Losses	(219,000)	(20,000)
Fair Value	$ 39,921,000	$ 52,330,000