COMPONENTS OF THE COMPANY'S CONDENSED CONSOLIDATED BALANCE SHEETS Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (1,361)	$ (2,382)	$ (1,689)	$ (2,139)
Other comprehensive income (loss) before reclassifications	7	263	319	(12)
Amounts reclassified from accumulated other comprehensive loss	18	31	34	63
Net-current period other comprehensive income (loss)	25	294	353	51
Ending balance	(1,336)	(2,088)	(1,336)	(2,088)
Unrealized Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	68	(665)	(266)	(427)
Other comprehensive income (loss) before reclassifications	257	226	591	(12)
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net-current period other comprehensive income (loss)	257	226	591	(12)
Ending balance	325	(439)	325	(439)
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(696)	(1,205)	(712)	(1,237)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive loss	18	31	34	63
Net-current period other comprehensive income (loss)	18	31	34	63
Ending balance	(678)	(1,174)	(678)	(1,174)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(733)	(512)	(711)	(475)
Other comprehensive income (loss) before reclassifications	(250)	37	(272)	0
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net-current period other comprehensive income (loss)	(250)	37	(272)	0
Ending balance	$ (983)	$ (475)	$ (983)	$ (475)