ACCRUED LIABILITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts Payable and Accrued Liabilities, Current [Abstract]
Accrued compensation	$ 2,916	$ 5,475
Accrued royalties	2,192	2,773
Accrued restructuring and one-time termination costs	820	1,578
Other accrued liabilities	14,048	21,535
Total accrued liabilities	$ 19,976	$ 31,361