Carrying amount as of the balance sheet date of cash collateral held for borrowed securities, for which the cash is restricted as to withdrawal or usage.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Derivatives and Hedging-Disclosures and Fair Value Measurements - Additional Information (Detail) gal in Millions	9 Months Ended
	Jun. 30, 2023 USD ($) gal	Jun. 30, 2022 gal	Sep. 30, 2022 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedging positions or payable amounts secured under credit facility \| $	$ 9,800,000		$ 0
Prepaid expense and other current assets
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregated cash posted as collateral in normal course of business \| $	1,800,000
Interest rate swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Value \| $	$ 56,400,000		54,000,000.0
Percentage of market risk exposure of long term debt	37.00%
Fair Value \| $	$ 1,500,000		$ 2,000,000
Call Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	6.1	37.3
Call Option \| Synthetic calls
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	41.6	17.6
Put Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	2.2	2.1
Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	5.0	5.5
Swap Contracts Bought \| Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	0.9	26.0
Future Contracts \| Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	10.9	0.5
Hedge its Internal Fuel Usage and Other Related Activities Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	5.4
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		0.4