COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
COMMITMENTS AND CONTINGENCIES
Long-term purchase commitment, amount									$ 2,800
Revenue recognition	$ 57,252	$ 52,979	$ 48,470	$ 49,774	$ 47,966	$ 51,337	$ 54,357	$ 52,887	208,475	$ 206,547	$ 201,576
Unapproved Products [Member]
COMMITMENTS AND CONTINGENCIES
Revenue recognition									16,900	20,700	24,900
Unapproved Products [Member] | Contract Customer [Member]
COMMITMENTS AND CONTINGENCIES
Revenue recognition									$ 2,800	$ 3,100	$ 2,000