Revenue and Accounts Receivable - Rollforward of Allowance for Doubtful Accounts (Details) $ in Thousands	12 Months Ended
Sep. 30, 2022 USD ($) state	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Revenue from Contract with Customer [Abstract]
Number of states excluded due to gas cost recovery mechanisms \| state	5
Percent of customers excluded due to gas cost recovery mechanisms	81.00%
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 64,471	$ 29,949	$ 15,899
Current period provisions	16,576	43,807	24,796
Write-offs charged against allowance	(32,885)	(11,019)	(12,698)
Recoveries of amounts previously written off	1,831	1,734	1,952
Ending balance	$ 49,993	$ 64,471	$ 29,949

Number of States With Ability To Recover Uncollectible Accounts Due To Gas Cost Recovery Mechanisms

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- Definition

Percent Of Customers With Ability To Recover Uncollectible Accounts Due To Gas Cost Recovery Mechanisms

+ References

No definition available.

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- Definition

Amount of allowance for credit loss on accounts receivable, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5074-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(4))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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- Definition

Amount of increase in allowance for credit loss on accounts receivable, from recovery.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of direct write-downs of accounts receivable charged against the allowance.

+ References

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- Definition

Amount of expense (reversal of expense) for expected credit loss on accounts receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(5))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

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- References

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