REVENUE RECOGNITION - DISAGGREGATED REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 10,624	$ 8,552	$ 24,489	$ 100,112
Contract with customer, asset, current	11,200		11,200		$ 9,000
Contract assets - long-term	6,033		6,033		$ 7,231
Decrease in contract with customer, asset			1,100
Fixed fee license revenue
Disaggregation of Revenue [Line Items]
Revenues	4,115	4,317	10,109	81,955
Per-Unit royalty revenue
Disaggregation of Revenue [Line Items]
Revenues	6,434	4,145	14,155	17,834
Total royalty and license revenue
Disaggregation of Revenue [Line Items]
Revenues	10,549	8,462	24,264	99,789
Development, services, and other revenue
Disaggregation of Revenue [Line Items]
Revenues	$ 75	$ 90	$ 225	$ 323