FINANCIAL INSTRUMENTS - Schedule of Fair Value on Recurring and Non-recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Current Assets:
Equity securities	$ 1,713	$ 1,520
Total current assets recorded at fair value	1,713	$ 1,520
Non-current Assets
Restricted Cash and Cash Equivalents, Noncurrent, Asset, Statement of Financial Position [Extensible List]		us-gaap:DisposalGroupIncludingDiscontinuedOperationAssetsNoncurrent
Restricted cash		$ 10
Total non-current assets recorded at fair value		10
Increase in fair value of equity securities	200
Level 1
Non-current Assets
Restricted cash		10
Total non-current assets recorded at fair value		10
Level 3
Current Assets:
Equity securities	1,713	1,520
Total current assets recorded at fair value	$ 1,713	$ 1,520