COMPONENTS OF THE COMPANY'S CONDENSED CONSOLIDATED BALANCE SHEETS Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (3,155)	$ (1,720)	$ (2,163)	$ (3,130)
Other comprehensive income (loss) before reclassifications	(147)	(684)	(1,116)	617
Amounts reclassified from accumulated other comprehensive income (loss)	53	49	30	158
Net-current period other comprehensive income (loss)	(94)	(635)	(1,086)	775
Ending balance	(3,249)	(2,355)	(3,249)	(2,355)
Unrealized Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(21)	2,197	890	583
Other comprehensive income (loss) before reclassifications	7	(633)	(904)	981
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0	0
Net-current period other comprehensive income (loss)	7	(633)	(904)	981
Ending balance	(14)	1,564	(14)	1,564
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,664)	(2,375)	(1,641)	(2,484)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	53	49	30	158
Net-current period other comprehensive income (loss)	53	49	30	158
Ending balance	(1,611)	(2,326)	(1,611)	(2,326)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,470)	(1,542)	(1,412)	(1,229)
Other comprehensive income (loss) before reclassifications	(154)	(51)	(212)	(364)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0	0
Net-current period other comprehensive income (loss)	(154)	(51)	(212)	(364)
Ending balance	$ (1,624)	$ (1,593)	$ (1,624)	$ (1,593)