Segment and Geographical Information (Details) $ in Millions	12 Months Ended
	Sep. 30, 2025 USD ($) segment	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Segment and Geographical Information
Number of reportable segments | segment	2
Net revenue	$ 2,673.8	$ 3,182.8	$ 2,826.0
Cost of goods sold	1,773.0	2,126.3	1,877.8
Segment Reporting, Other Segment Item, Amount	512.8	544.8	465.0
Adjusted EBITDA	388.0	511.7	483.2
Depreciation and amortization	138.5	158.0	125.6
Assets	4,467.1	5,238.7
Tangible long-lived assets, net	342.6	485.3
United States
Segment and Geographical Information
Net revenue	996.7	1,318.0	1,061.6
Tangible long-lived assets, net	86.1	186.1
China
Segment and Geographical Information
Net revenue	354.2	366.2	451.1
Tangible long-lived assets, net	125.9	134.5
China
Segment and Geographical Information
Net revenue	174.2	241.8	229.5
Tangible long-lived assets, net	42.1	37.1
India
Segment and Geographical Information
Net revenue	204.3	237.1	210.2
Tangible long-lived assets, net	6.6	35.6
All other countries
Segment and Geographical Information
Net revenue	944.4	1,019.7	873.6
Tangible long-lived assets, net	81.9	92.0
Corporate
Segment and Geographical Information
Net revenue	0.0	0.0	0.0
Cost of goods sold	0.0	0.0	0.0
Segment Reporting, Other Segment Item, Amount	56.6	53.8	59.6
Adjusted EBITDA	(56.6)	(53.8)	(59.6)
Assets	204.3	167.9
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment
Segment and Geographical Information
Depreciation and amortization	138.5	158.0	125.6
Advanced Process Solutions
Segment and Geographical Information
Net revenue	2,069.4	2,288.0	1,823.5
Advanced Process Solutions | Operating Segments
Segment and Geographical Information
Net revenue	2,069.4	2,288.0	1,823.5
Cost of goods sold	1,366.8	1,476.1	1,172.0
Segment Reporting, Other Segment Item, Amount	357.1	388.7	295.8
Adjusted EBITDA	345.5	423.2	355.7
Assets	3,438.1	3,470.8
Molding Technology Solutions
Segment and Geographical Information
Net revenue	604.4	894.8	1,002.5
Molding Technology Solutions | Operating Segments
Segment and Geographical Information
Net revenue	604.4	894.8	1,002.5
Cost of goods sold	406.2	650.2	705.8
Segment Reporting, Other Segment Item, Amount	99.1	102.3	109.6
Adjusted EBITDA	99.1	142.3	$ 187.1
Assets	$ 824.7	$ 1,600.0