COMPONENTS OF THE COMPANY'S CONDENSED CONSOLIDATED BALANCE SHEETS Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (1,336)	$ (2,088)	$ (1,689)	$ (2,139)
Other comprehensive income (loss) before reclassifications	235	(19)	554	(31)
Amounts reclassified from accumulated other comprehensive loss	17	31	51	94
Net-current period other comprehensive income (loss)	252	12	605	63
Ending balance	(1,084)	(2,076)	(1,084)	(2,076)
Unrealized Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	325	(439)	(266)	(427)
Other comprehensive income (loss) before reclassifications	208	165	799	153
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net-current period other comprehensive income (loss)	208	165	799	153
Ending balance	533	(274)	533	(274)
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(678)	(1,174)	(712)	(1,237)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive loss	17	31	51	94
Net-current period other comprehensive income (loss)	17	31	51	94
Ending balance	(661)	(1,143)	(661)	(1,143)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(983)	(475)	(711)	(475)
Other comprehensive income (loss) before reclassifications	27	(184)	(245)	(184)
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net-current period other comprehensive income (loss)	27	(184)	(245)	(184)
Ending balance	$ (956)	$ (659)	$ (956)	$ (659)