Derivatives and Hedging-Disclosures and Fair Value Measurements - Additional Information (Detail) gal in Millions	9 Months Ended
	Jun. 30, 2024 USD ($) gal	Jun. 30, 2023 gal	Sep. 30, 2023 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedging positions or payable amounts secured under credit facility | $	$ 2,900,000		$ 100,000
Prepaid expense and other current assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregated cash posted as collateral in normal course of business | $	1,500,000
Interest rate swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Value | $	$ 52,900,000		55,500,000
Percentage of market risk exposure of long term debt	40.00%
Fair Value | $	$ 600,000		$ 1,600,000
Call Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	3.8	6.1
Call Option | Synthetic calls
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	37.0	41.6
Put Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	3.5	2.2
Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	7.2	5.0
Swap Contracts Bought | Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	0.1	0.9
Future Contracts | Long
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	0.2
Future Contracts | Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	6.9	10.9
Hedge its Internal Fuel Usage and Other Related Activities Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	7.9	5.4