Segment Information (Property, Plant, and Equipment - Net by Geographical Area) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 922,043	$ 876,350
United States [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	872,947	826,225
Germany [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	24,541	24,468
Other Countries [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 24,555	$ 25,657