| **Exit Costs - Transportation Commitments - Income Statement Disclosures (Details) - USD ($) $ in Millions** | 3 Months Ended |
|--------------------------------------------------------------------------------------------------------------|----------------|
||
| **Long-term Purchase Commitment [Line Items]**                                                               |           |   |
| Revenue from Sales                                                                                           | $ 1,052        | $ 1,286 |
| Corporate                                                                                                    |           |   |
| **Long-term Purchase Commitment [Line Items]**                                                               |           |   |
| Revenue from Sales                                                                                           | 27             | 31 |
| Purchased Gas                                                                                                |           |   |
| **Long-term Purchase Commitment [Line Items]**                                                               |           |   |
| Revenue from Sales                                                                                           | 74             | 53 |
| Costs and Expenses                                                                                           | 87             | 57 |
| Purchased Gas | Corporate                                                                                    |           |   |
| **Long-term Purchase Commitment [Line Items]**                                                               |           |   |
| Revenue from Sales                                                                                           | 27             | 31 |
| Costs and Expenses                                                                                           | 27             | 30 |
| Utilized Firm Transportation Expense | Corporate                                                             |           |   |
| **Long-term Purchase Commitment [Line Items]**                                                               |           |   |
| Costs and Expenses                                                                                           | 15             | 5 |
| Unutilized Firm Transportation Expense | Corporate                                                           |           |   |
| **Long-term Purchase Commitment [Line Items]**                                                               |           |   |
| Costs and Expenses                                                                                           | 0              | 1 |
| Cost of Purchased Gas and Related Expense, Total                                                             |           |   |
| **Long-term Purchase Commitment [Line Items]**                                                               |           |   |
| Costs and Expenses                                                                                           | 87             | 57 |
| Cost of Purchased Gas and Related Expense, Total | Corporate                                                 |           |   |
| **Long-term Purchase Commitment [Line Items]**                                                               |           |   |
| Costs and Expenses                                                                                           | $ 42           | $ 36 |

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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.
+ 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
Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.
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| X                                                                                                                                                    |
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| X                                                                                                                                             |
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| X                                                                                                                                                       |
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