REVENUE RECOGNITION - DISAGGREGATED REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 7,596	$ 10,624	$ 19,521	$ 24,489
Fixed fee license revenue
Disaggregation of Revenue [Line Items]
Revenues	1,243	4,115	3,821	10,109
Per-Unit royalty revenue
Disaggregation of Revenue [Line Items]
Revenues	6,288	6,434	15,485	14,155
Total royalty and license revenue
Disaggregation of Revenue [Line Items]
Revenues	7,531	10,549	19,306	24,264
Development, services, and other revenue
Disaggregation of Revenue [Line Items]
Revenues	$ 65	$ 75	$ 215	$ 225