Amount of hedged item in hedging relationship. Excludes hedged asset or liability.

No definition available.

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

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- 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.

+ References

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- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

+ Details

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition

Percentage of an entity's outstanding debt that is designated as a hedged item in cash flow, fair value, or net investment hedge.

+ References

No definition available.

+ Details

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Derivatives and Hedging-Disclosures and Fair Value Measurements - Additional Information (Detail) gal in Millions, $ in Millions	9 Months Ended
	Jun. 30, 2026 USD ($) gal	Jun. 30, 2025 gal	Sep. 30, 2025 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedging positions or payable amounts secured under credit facility \| $			$ 1.3
Interest rate swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Value \| $	$ 71.9		74.5
Percentage of market risk exposure of long term debt	41.00%
Fair Value \| $	$ (0.1)		$ 0.6
Call Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	2.6	3.3
Call Option \| Synthetic calls
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	31.1	36.0
Put Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	1.7	3.7
Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	3.7	8.6
Swap Contracts Bought \| Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	1.2	0.7
Future Contracts \| Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	8.4	6.5
Hedge its Internal Fuel Usage and Other Related Activities Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	5.2	7.7