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REVENUE RECOGNITION - DISAGGREGATED REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 5,122	$ 85,416
Contract with customer, asset, current	8,000
Contract assets - long-term	7,154		$ 7,231
Increase (decrease) in contract with customer, asset	(1,000)
Total royalty and license revenue
Disaggregation of Revenue [Line Items]
Revenue	5,047	85,335
Fixed fee license revenue
Disaggregation of Revenue [Line Items]
Revenue	1,740	75,756
Per-unit royalty revenue
Disaggregation of Revenue [Line Items]
Revenue	3,307	9,579
Development, services, and other revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 75	$ 81