Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Allowance for doubtful accounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 3.9	$ 6.9	$ 8.2
Provision charged to expense, net of reversals	1.7	(2.9)	(0.7)
Write-offs, less recoveries, translation, other	0.0	(0.3)	(0.6)
Allowance for acquired receivables	0.0	0.2	0.0
Balance at end of year	5.6	3.9	6.9
Income tax valuation allowance
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	10.3	9.4	8.5
Provision charged to expense, net of reversals	(6.0)	(0.7)	(1.0)
Write-offs, less recoveries, translation, other	(2.0)	(0.2)	0.1
Balance at end of year	$ 18.3	$ 10.3	$ 9.4