CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowance	$ 21.8	$ 25.1
Preferred stock, authorized (in shares)	1,000,000	1,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, authorized (in shares)	199,000,000	199,000,000
Common stock, issued (in shares)	88,457,634	88,457,634
Treasury stock (in shares)	21,201,522	22,643,840