PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, net	$ 235,533	$ 219,492
Depreciation expense	44,668	44,659	$ 43,820
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	104,604	102,153
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	412,980	378,650
Buildings, Machinery and Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	517,584	480,803
Less accumulated depreciation	(335,346)	(305,613)
Total property, plant and equipment, net	182,238	175,190
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	16,845	19,705
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 36,450	$ 24,597