Fair Value Measurements (Schedule of the Carrying Values and Fair Values of Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Sep. 30, 2024
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including current portion and related party, carrying value	$ 15,084.7	$ 14,144.4
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including current portion and related party, fair value	14,588.8	13,897.3
Forward exchange contracts | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	51.6	100.8
Derivative liabilities	86.8	59.2
Forward exchange contracts | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	51.6	100.8
Derivative liabilities	86.8	59.2
Interest Rate Management Contracts | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	187.6	41.8
Derivative liabilities	37.1	41.4
Interest Rate Management Contracts | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	187.6	41.8
Derivative liabilities	$ 37.1	$ 41.4