CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2020	Sep. 30, 2019
Statement Of Financial Position [Abstract]
Allowance for Doubtful Accounts Receivable, Current	$ 58.2	$ 53.2
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	30,000,000.0	30,000,000.0
Preferred Stock, Shares Outstanding	0	0
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	600,000,000.0	600,000,000.0
Common Stock, Shares, Outstanding	259,200,000	257,800,000