Basis of Presentation and Accounting Policies - Narrative (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2023
Accounting Policies [Abstract]
Allowance for doubtful accounts	$ 20.1		$ 20.1		$ 16.8
Antidilutive share-based compensation awards (in shares)	0.5	0.4		0.5
Capital expenditures in accounts payable or other current liabilities at period end			7.3	$ 34.0
Outstanding purchase of common stock recorded in accounts payable			2.4	$ 0.8
Supplier finance program, obligation	$ 91.0		$ 91.0		$ 126.7