Derivatives - Summary of Gains (Losses) Recognized in Accumulated Other Comprehensive Loss, Net of Tax for Cash Flow Hedges (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Derivative [Line Items]
Gains (losses) recognized in accumulated other comprehensive loss, net of tax for cash flow hedges	[1]			$ 143.9	$ 335.8
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Natural Gas Commodity Hedge [Member]
Derivative [Line Items]
Gains (losses) recognized in accumulated other comprehensive loss, net of tax for cash flow hedges		$ 2.3	$ (3.4)	$ (5.4)	$ (15.3)

[1] All amounts are net of tax and noncontrolling interests.