Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 7.0	$ 6.9
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)	54,194,831	54,369,714
Treasury shares (in shares)	11,057,158	10,882,275