REVENUE RECOGNITION - Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 11,464	$ 10,624	$ 8,743	$ 5,122	$ 10,867	$ 8,552	$ 6,144	$ 85,416	$ 35,953	$ 110,979	$ 35,013
Contract with customer, asset, current	13,100				9,000				13,100	9,000
Contract assets - Long-term	$ 6,928				$ 7,231				6,928	7,231
Increase (decrease) in contract with customer, asset									3,900
Royalty and license
Disaggregation of Revenue [Line Items]
Revenue									35,643	110,557	34,089
Fixed fee license revenue
Disaggregation of Revenue [Line Items]
Revenue									12,627	83,573	12,575
Per-unit royalty revenue
Disaggregation of Revenue [Line Items]
Revenue									23,016	26,984	21,514
Development, services, and other
Disaggregation of Revenue [Line Items]
Revenue									$ 310	$ 422	$ 924