COMPONENTS OF THE COMPANY'S CONDENSED CONSOLIDATED BALANCE SHEETS (Changes in Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (3,737)	$ (2,163)
Other comprehensive income (loss) before reclassifications	(4,450)	(598)
Amounts reclassified from accumulated other comprehensive loss	18	(75)
Net-current period other comprehensive income (loss)	(4,432)	(673)
Ending balance	(8,169)	(2,836)
Unrealized Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,165)	890
Other comprehensive income (loss) before reclassifications	(4,181)	(580)
Amounts reclassified from accumulated other comprehensive loss	0	0
Net-current period other comprehensive income (loss)	(4,181)	(580)
Ending balance	(5,346)	310
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(674)	(1,641)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	18	(75)
Net-current period other comprehensive income (loss)	18	(75)
Ending balance	(656)	(1,716)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,898)	(1,412)
Other comprehensive income (loss) before reclassifications	(269)	(18)
Amounts reclassified from accumulated other comprehensive loss	0	0
Net-current period other comprehensive income (loss)	(269)	(18)
Ending balance	$ (2,167)	$ (1,430)