REVENUE RECOGNITION - NARRATIVE (Details) - USD ($) $ in Thousands	3 Months Ended					9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Increase (decrease) in royalty revenue recognized true-ups	$ (143)	$ 234	$ 149	$ (333)	$ (326)
Fixed fee license revenue recognized						$ 3,400	$ 5,700
Fixed fee license revenue | Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, payment terms						30 days
Fixed fee license revenue | Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, payment terms						45 days
Per-Unit royalty revenue | Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, payment terms						30 days
Per-Unit royalty revenue | Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, payment terms						60 days