Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 4.7	$ 5.6
Preferred shares, par value (in usd per share)	$ 0.01	$ 0.01
Preferred shares, authorized (in shares)	10,000,000	10,000,000
Preferred shares, issued (in shares)	0	0
Preferred shares, outstanding (in shares)	0	0
Common shares, par value (in usd per share)	$ 0.01	$ 0.01
Common shares, authorized (in shares)	300,000,000	300,000,000
Common shares, issued (in shares)	65,251,989	65,251,989
Common shares, outstanding (in shares)	54,300,084	54,206,746
Treasury shares (in shares)	10,951,905	11,045,243