REVENUE RECOGNITION - Disaggregated Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 30,456	$ 35,953
Royalty and license
Disaggregation of Revenue [Line Items]
Revenue	30,176	35,643
Fixed fee license revenue
Disaggregation of Revenue [Line Items]
Revenue	5,472	12,627
Per-unit royalty revenue
Disaggregation of Revenue [Line Items]
Revenue	24,704	23,016
Development, services, and other
Disaggregation of Revenue [Line Items]
Revenue	$ 280	$ 310