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, 2018		Sep. 30, 2017		Sep. 30, 2018		Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (2,088)		$ (2,419)		$ (2,139)		$ (2,710)
Other comprehensive income (loss) before reclassifications	(19)		49		(31)		242
Amounts reclassified from accumulated other comprehensive loss	31		50		94		148
Net-current period other comprehensive income (loss)	12		99		63		390
Ending balance	(2,076)		(2,320)		(2,076)		(2,320)
Unrealized Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(439)		(122)		(427)		(220)
Other comprehensive income (loss) before reclassifications	165		47		153		145
Amounts reclassified from accumulated other comprehensive loss	0		0		0		0
Net-current period other comprehensive income (loss)	165		47		153		145
Ending balance	(274)		(75)		(274)		(75)
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,174)		(1,838)		(1,237)		(1,936)
Other comprehensive income (loss) before reclassifications	0		0		0		0
Amounts reclassified from accumulated other comprehensive loss	31	[1]	50	[1]	94	[2]	148	[2]
Net-current period other comprehensive income (loss)	31		50		94		148
Ending balance	(1,143)		(1,788)		(1,143)		(1,788)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(475)		(459)		(475)		(554)
Other comprehensive income (loss) before reclassifications	(184)		2		(184)		97
Amounts reclassified from accumulated other comprehensive loss	0		0		0		0
Net-current period other comprehensive income (loss)	(184)		2		(184)		97
Ending balance	$ (659)		$ (457)		$ (659)		$ (457)

[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, 2018 and 2017.

[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, 2018 and 2017.