Financial Instruments (Gains and Losses Recognized In Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Net Investment Hedging Relationships
Tax effects	$ 34.3	$ (16.7)	$ (11.9)	$ 13.1
Net Amount Recognized in OCI	102.3	(223.8)	(521.7)	156.8
Derivatives in Cash Flow Hedging Relationships
Tax effects	(3.9)	(0.2)	18.1	(5.7)
Net Amount Recognized in OCI	(45.0)	82.3	20.7	(78.8)
Net investment hedges
Net Investment Hedging Relationships
Total Amount Recognized in OCI	(132.4)	80.6	62.3	(43.0)
Tax effects	32.1	(19.6)	(15.4)	10.5
Net Amount Recognized in OCI	(100.3)	61.0	46.9	(32.5)
Net investment hedges | Forward exchange contracts
Net Investment Hedging Relationships
Total Amount Recognized in OCI	(20.0)	31.6	33.9	(0.2)
Net investment hedges | Foreign currency debt
Net Investment Hedging Relationships
Total Amount Recognized in OCI	(112.4)	48.2	28.0	(41.7)
Net investment hedges | Cross currency interest rate swaps
Net Investment Hedging Relationships
Total Amount Recognized in OCI	0.0	0.8	0.4	(1.1)
Cash flow hedges
Derivatives in Cash Flow Hedging Relationships
Total Amount Recognized in OCI	(41.1)	82.5	2.6	(73.1)
Tax effects	(3.9)	(0.2)	18.1	(5.7)
Net Amount Recognized in OCI	(45.0)	82.3	20.7	(78.8)
Cash flow hedges | Forward exchange contracts
Derivatives in Cash Flow Hedging Relationships
Total Amount Recognized in OCI	43.4	(63.5)	(134.4)	51.6
Cash flow hedges | Forward exchange contracts, excluded components
Derivatives in Cash Flow Hedging Relationships
Total Amount Recognized in OCI	(4.8)	(3.4)	(6.3)	(12.4)
Cash flow hedges | Other
Derivatives in Cash Flow Hedging Relationships
Total Amount Recognized in OCI	$ (79.7)	$ 149.4	$ 143.3	$ (112.3)