Basis of Presentation and Accounting Policies - Narrative (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Accounting Policies [Abstract]
Allowance for doubtful accounts	$ 23.1		$ 23.1		$ 24.9
Allowance for certain customer returns, rebates and incentives	$ 7.5		$ 7.5		$ 11.9
Common shares excluded from computation of earnings per share amount (in shares)			2.6
Common shares included in computation of earnings per share if net income from continuing operations, amount (in shares)			1.7
Antidilutive share-based compensation awards (in shares)	0.9	1.0	0.9	1.0
Capital expenditures in accounts payable or other current liabilities at period end			$ 14.0	$ 17.6
Outstanding purchase of common stock recorded in accounts payable			$ 12.3	$ 7.0