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, 2017		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (2,419)		$ (1,527)		$ (2,710)		$ (1,851)
Other comprehensive income (loss) before reclassifications	49		(399)		242		(155)
Amounts reclassified from accumulated other comprehensive income (loss)	50		41		148		121
Net-current period other comprehensive income (loss)	99		(358)		390		(34)
Ending balance	(2,320)		(1,885)		(2,320)		(1,885)
Unrealized Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(122)		164		(220)		(97)
Other comprehensive income (loss) before reclassifications	47		(145)		145		116
Amounts reclassified from accumulated other comprehensive income (loss)	0		0		0		0
Net-current period other comprehensive income (loss)	47		(145)		145		116
Ending balance	(75)		19		(75)		19
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,838)		(1,504)		(1,936)		(1,584)
Other comprehensive income (loss) before reclassifications	0		0		0		0
Amounts reclassified from accumulated other comprehensive income (loss)	50	[1]	41	[1]	148	[2]	121	[2]
Net-current period other comprehensive income (loss)	50		41		148		121
Ending balance	(1,788)		(1,463)		(1,788)		(1,463)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(459)		(187)		(554)		(170)
Other comprehensive income (loss) before reclassifications	2		(254)		97		(271)
Amounts reclassified from accumulated other comprehensive income (loss)	0		0		0		0
Net-current period other comprehensive income (loss)	2		(254)		97		(271)
Ending balance	$ (457)		$ (441)		$ (457)		$ (441)

[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, 2017 and 2016.

[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, 2017 and 2016.