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 |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Interest Rate Contracts | ||||
| Derivative Instruments Gain Loss [Line Items] | ||||
| Income (loss) recognized in Other comprehensive income (loss) | $ 3.5 | $ (5.1) | $ 3.8 | $ 8.0 |
| Net income (loss) reclassified from Accumulated other comprehensive (loss) into Interest expense | 0.5 | 1.3 | 1.3 | 3.3 |
| Fuel Contracts [Member] | ||||
| Derivative Instruments Gain Loss [Line Items] | ||||
| Income (loss) recognized in Other comprehensive income (loss) | 2.1 | 0.0 | 1.6 | 0.0 |
| Net income (loss) reclassified from Accumulated other comprehensive (loss) into Interest expense | $ 0.0 | $ (0.2) | $ (0.2) | $ (0.5) |
| X | ||||||||||
- Definition The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments. No definition available.
|
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount, before tax and reclassification adjustment, of unrealized gain (loss) from increase (decrease) in instrument-specific credit risk of financial liability measured under fair value option. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|