Long-term and Short-term Debt - Schedule of Long-term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Long-term debt
Unamortized discount, capitalized lease obligations and other	$ (26.0)	$ (34.0)
Total debt	2,616.0	2,868.0
Less: Current portion	(2.0)	(307.0)
Long-term debt	$ 2,614.0	2,561.0
2.875% notes, payable in March 2025
Long-term debt
Stated interest rate (in percent)	2.875%
Debt instruments	$ 0.0	302.0
6.70% debentures, payable in January 2028
Long-term debt
Stated interest rate (in percent)	6.70%
Debt instruments	$ 250.0	250.0
3.50% notes, payable in March 2029
Long-term debt
Stated interest rate (in percent)	3.50%
Debt instruments	$ 425.0	425.0
1.75% notes, payable in August 2031
Long-term debt
Stated interest rate (in percent)	1.75%
Debt instruments	$ 450.0	450.0
6.25% debentures, payable in December 2037
Long-term debt
Stated interest rate (in percent)	6.25%
Debt instruments	$ 250.0	250.0
4.20% notes, payable in March 2049
Long-term debt
Stated interest rate (in percent)	4.20%
Debt instruments	$ 575.0	575.0
2.80% notes, payable in August 2061
Long-term debt
Stated interest rate (in percent)	2.80%
Debt instruments	$ 450.0	450.0
5.20% debentures, payable in January 2098
Long-term debt
Stated interest rate (in percent)	5.20%
Debt instruments	$ 200.0	200.0
Sensia loans from SLB, payable in October 2026
Long-term debt
Debt instruments	$ 42.0	$ 0.0