Derivatives and Hedging-Disclosures and Fair Value Measurements - Additional Information (Detail) gal in Millions	3 Months Ended
	Dec. 31, 2023 USD ($) gal	Dec. 31, 2022 gal	Sep. 30, 2023 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedging positions or payable amounts secured under credit facility | $	$ 15,700,000		$ 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 | $	1,600,000
Interest rate swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Value | $	$ 54,600,000		55,500,000
Percentage of market risk exposure of long term debt	38.00%
Fair Value | $	$ 600,000		$ 1,600,000
Call Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	8.8	23.2
Call Option | Synthetic calls
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	61.4	61.3
Put Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	6.6	4.3
Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	14.2	9.4
Swap Contracts Bought | Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	0.2	25.3
Future Contracts | Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	20.7	7.3
Hedge its Internal Fuel Usage and Other Related Activities Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	5.3	3.7