REVENUE RECOGNITION - DISAGGREGATED REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 7,173	$ 7,596	$ 25,342	$ 19,521
Fixed fee license revenue
Disaggregation of Revenue [Line Items]
Revenues	1,247	1,243	4,346	3,821
Per-unit royalty revenue
Disaggregation of Revenue [Line Items]
Revenues	5,821	6,288	20,671	15,485
Total royalty and license revenue
Disaggregation of Revenue [Line Items]
Revenues	7,068	7,531	25,017	19,306
Development, services, and other revenue
Disaggregation of Revenue [Line Items]
Revenues	$ 105	$ 65	$ 325	$ 215