Fair Value Measurements and Derivative Instruments - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Recurring - USD ($) $ in Millions	Dec. 31, 2025	Sep. 30, 2025
Carrying Value | Other Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets	$ 8.4	$ 7.9
Carrying Value | Other Liabilities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	10.8	9.5
Carrying Value | Other Liabilities | Interest Rate Derivative Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	1.9	1.5
Carrying Value | Accrued Expenses and Other Current Liabilities | Fuel Derivative Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	0.5	0.1
Investment Held by Rabbi Trust | Carrying Value | Other Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets	8.4	7.9
Investment Held by Rabbi Trust | Carrying Value | Other Liabilities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	8.4	7.9
Level 1 | Other Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets	8.4	7.9
Level 1 | Other Liabilities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	8.4	7.9
Level 1 | Other Liabilities | Interest Rate Derivative Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	0.0	0.0
Level 1 | Accrued Expenses and Other Current Liabilities | Fuel Derivative Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	0.0	0.0
Level 1 | Investment Held by Rabbi Trust | Other Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets	8.4	7.9
Level 1 | Investment Held by Rabbi Trust | Other Liabilities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	8.4	7.9
Level 2 | Other Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets	0.0	0.0
Level 2 | Other Liabilities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	2.4	1.6
Level 2 | Other Liabilities | Interest Rate Derivative Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	1.9	1.5
Level 2 | Accrued Expenses and Other Current Liabilities | Fuel Derivative Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	0.5	0.1
Level 2 | Investment Held by Rabbi Trust | Other Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets	0.0	0.0
Level 2 | Investment Held by Rabbi Trust | Other Liabilities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	0.0	0.0
Level 3 | Other Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets	0.0	0.0
Level 3 | Other Liabilities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	0.0	0.0
Level 3 | Other Liabilities | Interest Rate Derivative Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	0.0	0.0
Level 3 | Accrued Expenses and Other Current Liabilities | Fuel Derivative Contracts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	0.0	0.0
Level 3 | Investment Held by Rabbi Trust | Other Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets	0.0	0.0
Level 3 | Investment Held by Rabbi Trust | Other Liabilities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total liabilities	$ 0.0	$ 0.0