Earnings per Share (Schedule of Weighted-Average Shares Outstanding) (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Schedule Of Weighted Average Number Of Shares [Line Items]
Basic weighted-average shares outstanding (in shares)	51.1	52.5	51.3	53.5
Effect of dilutive securities (in shares)	0.7	0.6	0.6	0.6
Diluted weighted-average shares outstanding (in shares)	51.8	53.1	51.9	54.1
RSE and PRSE awards
Schedule Of Weighted Average Number Of Shares [Line Items]
Effect of dilutive securities (in shares)	0.7	0.6	0.6	0.6
Share options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive awards excluded from the calculation of diluted weighted-average shares outstanding (in shares)	0.8	1.0	1.0
RSE and PRSE awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive awards excluded from the calculation of diluted weighted-average shares outstanding (in shares)	0.0	0.5	0.0	0.3