v3.25.4
Goodwill and intangible assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Sep. 30, 2025
Finite-Lived Intangible Assets [Line Items]    
Gross Carrying Amount $ 786.4 $ 786.2
Trademarks and trade names - indefinite lived 640.8 640.8
Total Other intangible assets, net 1,427.2 1,427.0
Accumulated Amortization (429.7) (415.6)
Accumulated Impairment (5.9) (5.9)
Net Carrying Amount 350.8 364.7
Total Other intangible assets, net 991.6 1,005.5
Trade names    
Finite-Lived Intangible Assets [Line Items]    
Gross Carrying Amount 155.1 155.0
Accumulated Amortization (48.6) (46.4)
Accumulated Impairment 0.0 0.0
Net Carrying Amount 106.5 108.6
Customer Relationships    
Finite-Lived Intangible Assets [Line Items]    
Gross Carrying Amount 395.0 395.0
Accumulated Amortization (199.9) (193.3)
Accumulated Impairment (0.6) (0.6)
Net Carrying Amount 194.5 201.1
Patents    
Finite-Lived Intangible Assets [Line Items]    
Gross Carrying Amount 34.6 34.5
Accumulated Amortization (23.8) (23.3)
Accumulated Impairment 0.0 0.0
Net Carrying Amount 10.8 11.2
Proprietary Technology    
Finite-Lived Intangible Assets [Line Items]    
Gross Carrying Amount 172.5 172.5
Accumulated Amortization (139.4) (135.0)
Accumulated Impairment 0.0 0.0
Net Carrying Amount 33.1 37.5
Proprietary Formula    
Finite-Lived Intangible Assets [Line Items]    
Gross Carrying Amount 29.2 29.2
Accumulated Amortization (18.0) (17.6)
Accumulated Impairment (5.3) (5.3)
Net Carrying Amount $ 5.9 $ 6.3