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Risk Management Activities and Derivative Transactions Counterparty Credit Risk (Details) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Mar. 31, 2024 USD ($) | Mar. 31, 2024 USD ($) Customers | Mar. 31, 2023 | Sep. 30, 2023 USD ($)
Derivative |  |  |  |
Accounts Receivable, before Allowance for Credit Loss, Current | $ | $ 1,379 | $ 1,379 |  | $ 1,627
Two Largest Customer Percentage of Total Operating Revenue | 1500.00% |  | 1600.00% |
Moody's, A1 Rating [Member] |  |  |  |
Derivative |  |  |  |
Natural Gas Banking Counterparties Credit Rating |  | A1 |  |
Moody's, B1 Rating [Member] |  |  |  |
Derivative |  |  |  |
Natural Gas Banking Counterparties Credit Rating |  | B1 |  |
Moody's, A2 Rating |  |  |  |
Derivative |  |  |  |
Banking Counterparties Credit Rating |  | A2 |  |
Credit of Customers |  |  |  |
Derivative |  |  |  |
Number of customers that represent the percent of sales |  | 2 |  |
Number of customers that represent the percent of sales |  | 2 |  |

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