Risk Management Activities and Derivative Transactions Counterparty Credit Risk (Details)	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024
Derivative
Two Largest Customer Percentage of Total Operating Revenue	17.00%	17.00%
Moody's, A1 Rating
Derivative
Natural Gas Banking Counterparties Credit Rating	A1
Moody's, B1 Rating
Derivative
Natural Gas Banking Counterparties Credit Rating	B1
Moody's, A2 Rating
Derivative
Banking Counterparties Credit Rating	A2

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 20
-Name Accounting Standards Codification
-Section 25
-Paragraph 6A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480682/815-20-25-6A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-5

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