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Income Taxes - Components of Income Tax Expense (Details) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Disposal Groups, Including Discontinued Operations [Line Items] |  |  |
Current income tax expense(1) | $ 35 | $ 28 | $ 79
Deferred income tax expense (recovery) related to the origination and reversal of temporary differences | 22 | (61) | (110)
Deferred income tax expense resulting from changes in tax rates or laws | (31) | 0 | 110
Writedown (reversal of writedown) of deferred income tax assets | (9) | 27 | (15)
Current income tax expense | 35 | 28 | 79
Deferred income tax recovery | (18) | (34) | (15)
Income tax expense (recovery) | 17 | $ (6) | $ 64
Net deferred tax assets | 6 |  |
Tax Cuts and Jobs Act of 2017, change in rage, deferred tax asset, income tax expense (benefit) | 104 |  |
Tax Cuts and Jobs Act of 2017, change in tax Rate, deferred tax liability, income tax (expense) benefit | 110 |  |
Deferred tax expense (income) recognised in profit or loss | 1 |  |
Tax Cuts and Jobs Act of 2017, change in tax rate, deferred tax recovery | $ 111 |  |
Corporate tax rate | 26.50% | 26.80% | 26.80%
Solomon Power Station |  |  |
Disposal Groups, Including Discontinued Operations [Line Items] |  |  |
Current income tax expense(1) |  |  | $ 56

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