Earnings per Share (Schedule of Weighted-Average Shares Outstanding) (Details) - shares shares in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2024 |
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Schedule Of Weighted Average Number Of Shares [Line Items] | ||||
| Basic weighted-average shares outstanding (in shares) | 48.0 | 49.8 | 48.3 | 50.0 |
| Effect of dilutive securities (in shares) | 0.2 | 0.4 | 0.1 | 0.3 |
| Diluted weighted-average shares outstanding (in shares) | 48.2 | 50.2 | 48.4 | 50.3 |
| RSE and PRSE awards | ||||
| Schedule Of Weighted Average Number Of Shares [Line Items] | ||||
| Effect of dilutive securities (in shares) | 0.2 | 0.4 | 0.1 | 0.3 |
| 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) | 1.8 | 1.4 | 1.6 | 1.6 |