Income Taxes - Effective Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 159.6	$ 140.6	$ (205.5)	$ 406.5
Effective tax rate	17.90%	16.60%	36.60%	17.50%
Business and asset actions, including equity affiliate income			$ 2,958.8