ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Other long-term liabilities	$ 1,265	$ 1,465
Uncertain income tax positions recorded in noncurrent liabilities	200	200
Accrued lease restoration costs	400	600
Accrued benefit liability	367	451
Japan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accrued benefit liability	$ 400	$ 500