FAIR VALUE OF FINANCIAL INSTRUMENTS - Cost Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Investment balance before cumulative impairment as of January 1,		$ 3,005	$ 3,305	$ 3,305
Accumulated impairment as of January 1,			0	$ 0
Investment beginning balance after cumulative impairment as of January 1,		3,305	3,305
Disposal of investment in a privately held company	$ 900	(300)	0
Ending period balance		$ 3,005	$ 3,305