ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 732,345	$ 710,509	$ 691,618	$ 663,220	$ 639,890	$ 616,881	$ 691,618	$ 616,881
Other comprehensive (loss)/income	(2,861)	(1,508)	(1,084)	(536)	(2,895)	1,376	(5,453)	(2,055)
Ending balance	733,586	732,345	710,509	685,202	663,220	639,890	733,586	685,202
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(6,194)	(4,686)	(3,602)	(3,161)	(266)	(1,642)	(3,602)	(1,642)
Other comprehensive (loss)/income	(2,861)	(1,508)	(1,084)	(536)	(2,895)	1,376
Ending balance	(9,055)	$ (6,194)	(4,686)	$ (3,697)	$ (3,161)	$ (266)	(9,055)	$ (3,697)
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(4,285)				(4,285)
Other comprehensive (loss)/income							(3,513)
Ending balance	(7,798)						(7,798)
Cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			0				0
Other comprehensive (loss)/income							(1,956)
Ending balance	(1,956)						(1,956)
Postretirement benefit plan
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ 683				683
Other comprehensive (loss)/income							16
Ending balance	$ 699						$ 699