Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2016	Sep. 30, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 356.4	$ 336.2
Less accumulated depreciation	(24.4)	(13.6)
Property, plant and equipment, net	332.0	322.6
Facilities and equipment acquired under capital leases	39.0	25.2
Accumulated depreciation related to facilities and equipment acquired under capital leases	1.8	1.1
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	50.3	50.4
Plants and buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	103.4	89.8
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	132.9	130.5
Software and computer equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	49.3	49.0
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 20.5	$ 16.5