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, 2020		Sep. 30, 2019		Sep. 30, 2020		Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (1,720)		$ (1,336)		$ (3,130)		$ (1,689)
Other comprehensive income (loss) before reclassifications	(684)		235		617		554
Amounts reclassified from accumulated other comprehensive loss	49		17		158		51
Net-current period other comprehensive income (loss)	(635)		252		775		605
Ending balance	(2,355)		(1,084)		(2,355)		(1,084)
Unrealized Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	2,197		325		583		(266)
Other comprehensive income (loss) before reclassifications	(633)		208		981		799
Amounts reclassified from accumulated other comprehensive loss	0		0		0		0
Net-current period other comprehensive income (loss)	(633)		208		981		799
Ending balance	1,564		533		1,564		533
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(2,375)		(678)		(2,484)		(712)
Other comprehensive income (loss) before reclassifications	0		0		0		0
Amounts reclassified from accumulated other comprehensive loss	49	[1]	17	[1]	158	[2]	51	[2]
Net-current period other comprehensive income (loss)	49		17		158		51
Ending balance	(2,326)		(661)		(2,326)		(661)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,542)		(983)		(1,229)		(711)
Other comprehensive income (loss) before reclassifications	(51)		27		(364)		(245)
Amounts reclassified from accumulated other comprehensive loss	0		0		0		0
Net-current period other comprehensive income (loss)	(51)		27		(364)		(245)
Ending balance	$ (1,593)		$ (956)		$ (1,593)		$ (956)

[1] This component of accumulated other comprehensive income (loss) is included in the computation of net periodic pension cost for the three months ended September 30, 2020 and 2019.

[2] This component of accumulated other comprehensive income (loss) is included in the computation of net periodic pension cost for the nine months ended September 30, 2020 and 2019.