Financial Instruments (Currency Price Risk Management Instruments) (Details) - Forward exchange contracts - USD ($) $ in Millions |
6 Months Ended | 12 Months Ended |
|---|---|---|
Mar. 31, 2024 |
Sep. 30, 2023 |
|
| Derivative [Line Items] | ||
| US$ Notional | $ 6,238.4 | $ 6,036.6 |
| Years Average Maturity | 9 months 18 days | 10 months 24 days |
| Designated as hedging instrument | Cash flow hedges | ||
| Derivative [Line Items] | ||
| US$ Notional | $ 4,576.1 | $ 4,463.2 |
| Years Average Maturity | 7 months 6 days | 8 months 12 days |
| Designated as hedging instrument | Net investment hedges | ||
| Derivative [Line Items] | ||
| US$ Notional | $ 884.4 | $ 864.0 |
| Years Average Maturity | 2 years | 2 years 6 months |
| Not designated as hedging instrument | ||
| Derivative [Line Items] | ||
| US$ Notional | $ 777.9 | $ 709.4 |
| Years Average Maturity | 3 months 18 days | 3 months 18 days |