Derivatives and Hedging-Disclosures and Fair Value Measurements - Additional Information (Detail) gal in Millions	12 Months Ended
	Sep. 30, 2025 USD ($) gal	Sep. 30, 2024 USD ($) gal
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedging positions and payable amounts secured under credit facility	$ 1,300,000	$ 14,200,000
Prepaid expense and other current assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregated cash posted as collateral in normal course of business	1,600,000
Interest rate swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Value	74,500,000	52,000,000
Fair Value	$ (600,000)	$ (300,000)
Percentage of market risk exposure of long term debt	39.00%
Call Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume | gal	5.4	6.0
Notional Value	$ 15,100,000	$ 18,200,000
Fair Value	$ 100,000
Call Option | Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value		$ 100,000
Call Option | Synthetic calls
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume | gal	49.0	52.1
Notional Value	$ 113,900,000	$ 133,900,000
Fair Value	$ (1,900,000)	$ (9,200,000)
Put Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume | gal	6.0	7.1
Notional Value	$ 9,800,000	$ 12,700,000
Fair Value		$ 300,000
Put Option | Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value	$ 100,000
Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume | gal	13.4	12.2
Notional Value	$ 29,900,000	$ 29,400,000
Fair Value	$ 400,000	$ (2,800,000)
Future Contracts | Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume | gal	8.6	6.2
Notional Value	$ 19,700,000	$ 14,000,000
Fair Value		$ (600,000)
Future Contracts | Short | Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value	$ 100,000
Hedge its Internal Fuel Usage and Other Related Activities Call Options and Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume | gal	7.8	8.4
Notional Value	$ 16,200,000	$ 20,300,000
Fair Value	$ 800,000	$ (2,300,000)
Swap Contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume | gal	1.1	0.7
Notional Value	$ 2,500,000	$ 1,400,000
Swap Contracts | Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value	$ 100,000	$ 100,000