FAIR VALUE MEASUREMENTS (Details) - Level 1 - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Adjusted cost	$ 30,024,000	$ 41,012,000
Unrealized gains	13,000	15,000
Unrealized losses	0	0
Market value	30,037,000	41,027,000
U.S. Treasury Securities Considered Cash Equivalents [Member]
Adjusted cost	0	9,998,000
Unrealized gains	0	0
Unrealized losses	0	0
Market value	0	9,998,000
U.S. Treasury Securities in Short-term Investments [Member]
Adjusted cost	29,989,000	24,979,000
Unrealized gains	13,000	15,000
Unrealized losses	0	0
Market value	30,002,000	24,994,000
Money Market Funds [Member]
Adjusted cost	35,000	6,035,000
Unrealized gains	0	0
Unrealized losses	0	0
Market value	$ 35,000	$ 6,035,000