ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other long-term liabilities	$ 2,302	$ 1,265
Uncertain income tax positions recorded in noncurrent liabilities	200	200
Accrued lease restoration costs	400	400
Accrued benefit liability	388	367
Japan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accrued benefit liability	$ 400	$ 400