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Fair Value of Financial Instruments and Risk Management - Volume of Derivative Activity (Details) GJ in Millions | 12 Months Ended
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Dec. 31, 2024 GWh GJ | Dec. 31, 2023 GWh GJ
Electricity swap contracts |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Energy measure (gwh) | GWh | 774 | 628
Electricity power purchase contracts |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Energy measure (gwh) | GWh | 430 | 588
Gas swap contracts |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Energy measure (gwh) | GJ | 236 | 228
Gas supply contracts |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Energy measure (gwh) | GJ | 105 | 134
Wholesale trading contracts |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Energy measure (gwh) | GWh | 1,499 | 1,310
Gas swap contracts |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Energy measure (gwh) | GJ | 3 | 3

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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. + Details
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- Definition Nominal energy measure used to calculate payments on a derivative instrument. + References No definition available. + Details
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