Financial Instruments (Gains and Losses Recognized In Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Net Investment Hedging Relationships
Tax effects	$ (16.7)	$ 10.6	$ 13.1	$ 48.6
Net Amount Recognized in OCI	(223.8)	51.0	156.8	560.6
Derivatives in Cash Flow Hedging Relationships
Tax effects	(0.2)	0.6	(5.7)	(37.6)
Net Amount Recognized in OCI	82.3	(14.6)	(78.8)	106.4
Net investment hedges
Net Investment Hedging Relationships
Total Amount Recognized in OCI	80.6	(54.1)	(43.0)	(227.1)
Tax effects	(19.6)	13.3	10.5	55.8
Net Amount Recognized in OCI	61.0	(40.8)	(32.5)	(171.3)
Net investment hedges | Forward exchange contracts
Net Investment Hedging Relationships
Total Amount Recognized in OCI	31.6	(15.3)	(0.2)	(62.4)
Net investment hedges | Foreign currency debt
Net Investment Hedging Relationships
Total Amount Recognized in OCI	48.2	(35.6)	(41.7)	(150.9)
Net investment hedges | Cross currency interest rate swaps
Net Investment Hedging Relationships
Total Amount Recognized in OCI	0.8	(3.2)	(1.1)	(13.8)
Cash flow hedges
Derivatives in Cash Flow Hedging Relationships
Total Amount Recognized in OCI	82.5	(15.2)	(73.1)	144.0
Tax effects	(0.2)	0.6	(5.7)	(37.6)
Net Amount Recognized in OCI	82.3	(14.6)	(78.8)	106.4
Cash flow hedges | Forward exchange contracts
Derivatives in Cash Flow Hedging Relationships
Total Amount Recognized in OCI	(63.5)	5.3	51.6	194.1
Cash flow hedges | Forward exchange contracts, excluded components
Derivatives in Cash Flow Hedging Relationships
Total Amount Recognized in OCI	(3.4)	(5.9)	(12.4)	(11.5)
Cash flow hedges | Other
Derivatives in Cash Flow Hedging Relationships
Total Amount Recognized in OCI	$ 149.4	$ (14.6)	$ (112.3)	$ (38.6)