Summary of Significant Accounting Policies - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Property, Plant and Equipment
Impairment recognized	$ 0	$ 0	$ 0
Buildings and improvements
Property, Plant and Equipment
Estimated economic useful lives	40 years
Machinery and equipment | Minimum
Property, Plant and Equipment
Estimated economic useful lives	5 years
Machinery and equipment | Maximum
Property, Plant and Equipment
Estimated economic useful lives	14 years
Land improvements
Property, Plant and Equipment
Estimated economic useful lives	20 years