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Risk Management Activities - Effect of Hedges (Details) MWh in Thousands, $ in Millions, $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2024 CAD ($) MWh | Dec. 31, 2023 CAD ($) MWh | Dec. 31, 2024 USD ($) MWh | Dec. 31, 2023 USD ($) MWh
Disclosure of detailed information about hedging instruments [line items] |  |  |  |
Fair value asset |  | $ 5 |  |
Fair value liability | $ 7 |  |  |
Physical power sales | Cash flow hedges | Commodity risk management |  |  |  |
Disclosure of detailed information about hedging instruments [line items] |  |  |  |
Notional amount (MMWH) | MWh | 2,628 | 5,966 | 2,628 | 5,966
Fair value liability | $ 45 | $ (205) |  |
Gain (loss) on hedge ineffectiveness | 114 | (114) |  |
Foreign-denominated Debt | Net Investment Hedge | Currency risk |  |  |  |
Disclosure of detailed information about hedging instruments [line items] |  |  |  |
Fair value asset | 431 | 489 |  |
Gain (loss) on hedge ineffectiveness | $ 0 | $ 0 |  |
Foreign-denominated Debt | Net Investment Hedge | Currency risk | USD |  |  |  |
Disclosure of detailed information about hedging instruments [line items] |  |  |  |
Notional amount |  |  | $ 300 | $ 370

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