Income Taxes (Effective Tax Rate) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 158.7	$ (505.8)	$ 318.1	$ (365.1)
Effective tax rate	18.00%	22.50%	18.30%	25.10%
Business and asset actions, including equity affiliate income		$ 2,900.0		$ 2,900.0