Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Current allowance for credit losses
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 4.6	$ 0.3	$ 0.3
Charged to expenses	(0.6)	4.5	0.0
Charged to other accounts	(3.4)	(0.2)	0.0
Deductions	0.0	0.0	0.0
Balance at end of period	0.6	4.6	0.3
Allowances for loan losses
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	2.2	2.1	2.0
Charged to expenses	0.0	0.0	0.0
Charged to other accounts	0.2	0.1	0.1
Deductions	0.0	0.0	0.0
Balance at end of period	2.4	2.2	2.1
Inventory excess and obsolete reserves
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	2.0	0.8	0.6
Charged to expenses	(0.3)	1.2	0.2
Charged to other accounts	(0.6)	0.0	0.0
Deductions	0.0	0.0	0.0
Balance at end of period	1.1	2.0	0.8
Deferred tax asset valuation allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	33.3	31.8	29.7
Charged to expenses	(30.3)	1.5	0.9
Charged to other accounts	0.0	0.0	1.2
Deductions	0.0	0.0	0.0
Balance at end of period	$ 3.0	$ 33.3	$ 31.8