ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS), Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in accumulated other comprehensive income (loss) [Abstract]
Net foreign currency translation adjustment	$ 1,363	$ 541
Net change in postretirement benefit plan (see Note 15 for further information)
Amortization of prior service cost (credit)	18	19
Amortization of gain	(1)	(4)
Total before tax	17	15
Tax	(4)	(5)
Net of tax	13	10
Other comprehensive income	$ 1,376	$ 551