Derivatives and Hedging-Disclosures and Fair Value Measurements - Additional Information (Detail) gal in Millions	9 Months Ended
	Jun. 30, 2022 USD ($) gal	Jun. 30, 2021 gal	Sep. 30, 2021 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedging positions or payable amounts secured under credit facility | $	$ 0		$ 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 | $	100,000
Interest rate swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Value | $	$ 55,300,000		59,000,000.0
Percentage of market risk exposure of long term debt	58.00%
Fair Value | $	$ 1,300,000		$ (1,600,000)
Call Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	37.3	5.3
Call Option | Synthetic calls
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	17.6	57.2
Put Option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	2.1	2.9
Swap Contracts Bought
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	5.5	8.9
Swap Contracts Bought | Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	26.0
Future Contracts | Long
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume		3.8
Future Contracts | Short
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative activity volume	0.5	21.5
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	3.6