Fair Value Measurements and Derivative Instruments - Summary of Effects on Consolidated Financial Statements of Designated As Cash Flow Hedges (Details) - Cash Flow Hedges - Designated - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Interest Rate Contracts
Derivative Instruments Gain Loss [Line Items]
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest Expense	Interest Expense	Interest Expense
Income (loss) recognized in Other comprehensive income	$ 36.1	$ 6.1	$ (0.6)
Net gain (loss) reclassified from Accumulated other comprehensive loss into Interest expense	$ 15.2	$ (0.5)	$ (6.8)
Fuel Swap Contracts
Derivative Instruments Gain Loss [Line Items]
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration]	Cost of Goods and Services Sold	Cost of Goods and Services Sold	Cost of Goods and Services Sold
Income (loss) recognized in Other comprehensive income	$ 0.0	$ 0.2	$ 3.5
Net gain (loss) reclassified from Accumulated other comprehensive loss into Interest expense	$ 0.0	$ 1.5	$ 2.3