CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2019	Sep. 30, 2018
Statement Of Financial Position [Abstract]
Allowance for Doubtful Accounts Receivable, Current	$ 46.9	$ 49.7
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	30,000,000	30,000,000
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	600,000,000
Common Stock, Shares, Outstanding	256,900,000	253,500,000