Goodwill and intangible assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2023	Sep. 30, 2022
Finite-Lived Intangible Assets [Line Items]
Cumulative translation adjustment	$ 20.1
Gross Carrying Amount	780.8	$ 777.3
Trademarks and trade names - indefinite lived	763.3	762.5
Total Other intangible assets, net	1,544.1	1,539.8
Accumulated Amortization	(291.1)	(244.0)
Net Carrying Amount	489.7	533.3
Total Other intangible assets, net	1,253.0	1,295.8
Trademarks and trade names - indefinite lived
Finite-Lived Intangible Assets [Line Items]
Trademarks and trade names - indefinite lived		762.5
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	142.6	141.8
Accumulated Amortization	(27.6)	(21.4)
Net Carrying Amount	115.0	120.4
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	394.6	393.5
Accumulated Amortization	(133.4)	(112.6)
Net Carrying Amount	261.2	280.9
Patents
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	34.2	33.4
Accumulated Amortization	(17.6)	(15.7)
Net Carrying Amount	16.6	17.7
Proprietary technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	172.5	172.5
Accumulated Amortization	(95.6)	(81.5)
Net Carrying Amount	76.9	91.0
Proprietary Formula
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	29.2	29.2
Accumulated Amortization	(9.2)	(6.3)
Net Carrying Amount	20.0	22.9
Vendor Relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7.7	6.9
Accumulated Amortization	(7.7)	(6.5)
Net Carrying Amount	$ 0.0	$ 0.4