ACCRUED LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Accounts Payable and Accrued Liabilities, Current [Abstract]
Accrued compensation	$ 4,205			$ 7,345
Accrued royalties	4,715			17,370
Accrued restructuring and one-time termination costs	1,835	$ 5,500	$ 6,820	9,483
Other accrued liabilities	15,320			26,298
Total accrued liabilities	$ 26,075			$ 60,496