Summary of Significant Accounting Policies - Property (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment [Line Items]
Depreciation	$ 1.6	$ 2.5	$ 2.9
Property, Plant and Equipment, Net
Property, at cost	21.5	21.6
Accumulated depreciation	(13.5)	(12.7)
Property, net	8.0	8.9
Europe
Property, Plant and Equipment [Line Items]
Long-lived assets	6.0	6.6
Land and land improvements
Property, Plant and Equipment, Net
Property, at cost	0.7	0.8
Building and building improvements
Property, Plant and Equipment, Net
Property, at cost	$ 5.4	5.5
Building and building improvements | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	1 year
Building and building improvements | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	33 years
Machinery and equipment
Property, Plant and Equipment, Net
Property, at cost	$ 12.6	12.6
Machinery and equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	2 years
Machinery and equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	13 years
Computer software, intangible asset
Property, Plant and Equipment, Net
Property, at cost	$ 2.3	2.1
Computer software, intangible asset | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	1 year
Computer software, intangible asset | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Construction in progress
Property, Plant and Equipment, Net
Property, at cost	$ 0.5	$ 0.6