Basis of Presentation and Accounting Policies - Narrative (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018
Accounting Policies [Abstract]
Allowance for doubtful accounts	$ 18.6		$ 17.1
Allowance for certain customer returns, rebates and incentives	$ 13.1		$ 8.7
Antidilutive share-based compensation awards (in shares)	1.8	2.8
Shares to be included if recorded net income from continuing operations	1.9
Capital expenditures in accounts payable or other current liabilities at period end	$ 17.1	$ 13.0
Outstanding purchase of common stock recorded in accounts payable	$ 16.0	$ 17.8