Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Allowance for doubtful accounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 4.6	$ 5.6	$ 3.9
Provision charged to expense, net of reversals	0.1	(0.8)	1.7
Write-offs, less recoveries, translation, other	0.1	(0.2)	0.0
Allowance for acquired receivables	0.0	0.0	0.0
Balance at end of year	4.8	4.6	5.6
Income tax valuation allowance
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	21.5	18.3	10.3
Provision charged to expense, net of reversals	(0.3)	4.6	6.0
Write-offs, less recoveries, translation, other	(0.3)	1.4	(2.0)
Balance at end of year	$ 20.9	$ 21.5	$ 18.3