Fair Value Measurements and Derivative Instruments - Additional Information (Details) FuelGal in Millions, $ in Millions	12 Months Ended
Sep. 30, 2021 USD ($) FuelGal	Sep. 30, 2020 USD ($)
Derivative [Line Items]
Number of outstanding fuel contracts \| FuelGal	5.3
Interest Rate Contracts
Derivative [Line Items]
Notional amount	$ 500.0	$ 980.0
Net deferred losses on interest rate swap net of taxes expected to be recognized over the next 12 months	$ 2.2
Maximum
Derivative [Line Items]
Percentage of participants compensation deferred	70.00%

Deferred compensation arrangement percentage of participants compensation deferred.

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- Definition

Net deferred losses net of taxes expected to be recognized in interest expense.

+ References

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- Definition

Number of outstanding fuel contracts.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

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