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Employee Future Benefits - Components Recognized in OCI and Regulatory Assets (Details) - CAD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023
DBP Plans |  |
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract] |  |
Current year net actuarial (gains) losses | $ (1) | $ 4
Past service credits/plan amendments | 0 | 0
Foreign currency translation | 0 | (1)
Income tax recovery | 0 | (1)
Total recognized in comprehensive income | (1) | 2
Regulatory Assets, Pension and Other Postretirement Benefit Plans [Abstract] |  |
Current year net actuarial (gains) losses | (142) | 78
Amortization of actuarial gains | 1 | 9
Amortization of past service credits | 1 | 2
Foreign currency translation | (2) | (1)
Regulatory adjustments | 23 | (5)
Total recognized in regulatory (liabilities) assets | (119) | 83
OPEB Plans |  |
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract] |  |
Current year net actuarial (gains) losses | (1) | 1
Past service credits/plan amendments | 0 | (1)
Foreign currency translation | 0 | 0
Income tax recovery | 0 | 0
Total recognized in comprehensive income | (1) | 0
Regulatory Assets, Pension and Other Postretirement Benefit Plans [Abstract] |  |
Current year net actuarial (gains) losses | (72) | (40)
Amortization of actuarial gains | 16 | 18
Amortization of past service credits | 1 | 1
Foreign currency translation | (12) | 2
Regulatory adjustments | 2 | (5)
Total recognized in regulatory (liabilities) assets | $ (65) | $ (24)

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