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Risk Management Activities and Derivative Transactions Counterparty Credit Risk (Details) | 12 Months Ended
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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 |

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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 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 + Details
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