MYOSCIENCE ACQUISITION (Details) - USD ($) $ in Thousands	Apr. 09, 2019	Sep. 30, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Contingent consideration, current		$ 5,406	$ 18,179
Achievement of Regulatory Milestone
Business Acquisition [Line Items]
Acquisition-related contingent consideration		15,000
Myoscience Acquisition
Business Acquisition [Line Items]
Total consideration transferred	$ 147,500
Initial cash payment	119,000
Fair value of contingent consideration	28,500
Contingent consideration	$ 100,000
Contingent consideration, current		58,000
Payment term	60 days
Acquisition-related contingent consideration		$ 21,600