Property, Plant, and Equipment, Net (Property, Plant, and Equipment - Net) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 1,481,552		$ 1,481,552		$ 1,442,896
Less accumulated depreciation	(538,119)		(538,119)		(520,853)
Property, Plant and Equipment, Net, Total	943,433		943,433		922,043
Depreciation expense	15,754	$ 13,663	30,581	$ 26,118
Capitalized interest	633	$ 481	1,234	$ 953
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	88,595		88,595		88,326
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	516,687		516,687		514,453
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	18,303		18,303		16,142
Machinery and Equipment, Excluding Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	575,695		575,695		543,641
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	122,663		122,663		124,723
Office furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	24,661		24,661		24,308
Other Capitalized Property Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	19,397		19,397		19,393
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 115,551		$ 115,551		$ 111,910