Basis of Presentation and Accounting Policies - Narrative (Details) - USD ($) shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
	Oct. 01, 2019	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Allowance for doubtful accounts		$ 14.3		$ 14.3		$ 15.2
Allowance for certain customer returns, rebates and incentives		$ 8.9		$ 8.9		8.1
Antidilutive share-based compensation awards (in shares)		0.2	2.3	0.2	2.3
Capital expenditures in accounts payable or other current liabilities at period end				$ 15.5	$ 18.5
Outstanding purchase of common stock recorded in accounts payable				2.8	$ 2.0
Operating lease right-of-use assets		$ 347.0		$ 347.0		$ 342.9
Accounting Standards Update 2016-02
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Operating lease right-of-use assets	$ 316.0
Operating lease liability	329.0
Accumulated other comprehensive loss
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Reclassification from AOCI to retained earnings	$ 147.0