Debt (Interest) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Debt Disclosure [Abstract]
Interest incurred	$ 292.9	$ 169.0	$ 170.1
Less: Capitalized interest	115.4	41.0	28.3
Interest expense	177.5	128.0	141.8
Cash paid for interest, net of amounts capitalized	$ 131.5	$ 128.5	$ 150.4