Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 14,530	$ 13,259	$ 42,518	$ 38,645
Maintenance and repair expense	6,238	$ 5,395	17,620	$ 15,905
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	489,540		489,540		$ 447,126
Less: accumulated depreciation	(200,362)		(200,362)		(167,083)
Property, plant and equipment, net	289,178		289,178		280,043
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	358,603		358,603		338,056
Land and buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	82,406		82,406		84,282
Construction in process
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 48,531		$ 48,531		$ 24,788