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Decommissioning and Other Provisions - Decommissioning and Restoration - Narrative (Details) $ in Millions | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2024 CAD ($) | Dec. 31, 2023 CAD ($) | Dec. 31, 2024 USD ($) | Dec. 04, 2024 CAD ($) | Dec. 31, 2023 USD ($)
Disclosure of detailed information about borrowings [line items] |  |  |  |  |
Undiscounted cash amount | $ 1,800,000,000 |  |  |  |
Increase in PP&E | 18,000,000 | $ 31,000,000 |  |  |
Increase through change in estimated cash flows | 41,000,000 | (89,000,000) |  |  |
Revisions in discount rates | 35,000,000 | 52,000,000 |  |  |
Reversal of impairment loss | 17,000,000 | 21,000,000 |  |  |
Heartland Generation |  |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |  |
Decommissioning provisions |  |  |  | $ 101,000,000 |
Other provisions |  |  |  | $ 55,000,000 |
Heartland Generation | Gas |  |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |  |
Other provisions | 47,000,000 |  |  |  |
Minimum |  |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |  |
Revisions in discount rates | 5.3 | 0.060 |  |  |
Maximum |  |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |  |
Revisions in discount rates | 0.084 | 0.090 |  |  |
Decommissioning and restoration |  |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |  |
Decommissioning and restoration provision | 35,000,000 | 52,000,000 |  |  |
Gas |  |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |  |
Decommissioning and restoration provision | 14,000,000 | 34,000,000 |  |  |
Centralia Coal Mine | Surety Bonds |  |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |  |
Bonds issued |  |  | $ 147 |  | $ 147
Alberta Mine | Letters Of Credit |  |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |  |
Bonds issued | 194,000,000 | 188,000,000 |  |  |
Decommissioning and restoration |  |  |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |  |  |
Increase in PP&E | 7,000,000 | 55,000,000 |  |  |
Increase through change in estimated cash flows | 21,000,000 | (89,000,000) |  |  |
Revisions in discount rates | $ 35,000,000 | $ 52,000,000 |  |  |

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