COMPONENTS OF THE COMPANY'S CONDENSED CONSOLIDATED BALANCE SHEETS Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (3,130)	$ (1,689)
Other comprehensive income (loss) before reclassifications	(1,235)	312
Amounts reclassified from accumulated other comprehensive loss	51	16
Net-current period other comprehensive income (loss)	(1,184)	328
Ending balance	(4,314)	(1,361)
Unrealized Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	583	(266)
Other comprehensive income (loss) before reclassifications	(952)	334
Amounts reclassified from accumulated other comprehensive loss	0	0
Net-current period other comprehensive income (loss)	(952)	334
Ending balance	(369)	68
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(2,484)	(712)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	51	16
Net-current period other comprehensive income (loss)	51	16
Ending balance	(2,433)	(696)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,229)	(711)
Other comprehensive income (loss) before reclassifications	(283)	(22)
Amounts reclassified from accumulated other comprehensive loss	0	0
Net-current period other comprehensive income (loss)	(283)	(22)
Ending balance	$ (1,512)	$ (733)