ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 710,509	$ 691,618	$ 639,890	$ 616,881	$ 691,618	$ 616,881
Other comprehensive (loss)/income	(1,508)	(1,084)	(2,895)	1,376	(2,592)	(1,519)
Ending balance	732,345	710,509	663,220	639,890	732,345	663,220
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4,686)	(3,602)	(266)	(1,642)	(3,602)	(1,642)
Other comprehensive (loss)/income	(1,508)	(1,084)	(2,895)	1,376
Ending balance	(6,194)	(4,686)	$ (3,161)	$ (266)	(6,194)	$ (3,161)
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(4,285)			(4,285)
Other comprehensive (loss)/income					(1,304)
Ending balance	(5,589)				(5,589)
Cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		0			0
Other comprehensive (loss)/income					(1,299)
Ending balance	(1,299)				(1,299)
Postretirement benefit plan
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ 683			683
Other comprehensive (loss)/income					11
Ending balance	$ 694				$ 694