Supplemental Financial Statement Information (Supplemental Statement of Income Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Financial Statement Related Disclosures [Line Items]
Interest income	$ (2.4)	$ (1.1)	$ (8.0)	$ (1.3)
Foreign currency exchange gain (loss)	5.9	4.5	29.6	3.5
Pension cost other than service costs	1.0	0.6	2.0	1.3
Debt Securities, Available-for-Sale, Gain (Loss)	1.0	0.0	1.0	0.0
Transition services agreement income	0.0	0.0	(1.0)	0.0
Other	0.0	(3.2)	0.9	(4.1)
Total Other items, net	5.5	$ 0.8	24.5	$ (0.6)
ARGENTINA
Financial Statement Related Disclosures [Line Items]
Foreign currency exchange gain (loss)	$ 1.0		22.0
ARGENTINA | Nonoperating Income (Expense)
Financial Statement Related Disclosures [Line Items]
Foreign currency exchange gain (loss)			$ 21.0