Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 26.9	$ 27.3
Common stock, shares authorized	450,000,000	450,000,000
Common stock, shares issued	173,987,691	173,894,141