Income Taxes - Significant Components of Deferred Income Tax Assets (Liabilities) (Details) - CAD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Unrecognized deferred income tax assets	$ (21)	$ (50)
Net deferred tax liabilities	(365)	(302)
Cost \| Non-capital losses
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred income tax asset (liability), before write-down of deferred income tax assets	88	244
Cost \| Future decommissioning and restoration costs
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred income tax asset (liability), before write-down of deferred income tax assets	111	119
Cost \| Property, plant and equipment
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred income tax asset (liability), before write-down of deferred income tax assets	(605)	(553)
Cost \| Risk management assets and liabilities, net
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred income tax asset (liability), before write-down of deferred income tax assets	144	193
Cost \| Employee future benefits and compensation plans
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred income tax asset (liability), before write-down of deferred income tax assets	50	48
Cost \| Foreign exchange differences on US-denominated debt
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred income tax asset (liability), before write-down of deferred income tax assets	12	13
Cost \| Other taxable temporary differences
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred income tax asset (liability), before write-down of deferred income tax assets	(8)	(5)
Accumulated impairment
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Net deferred income tax asset (liability), before write-down of deferred income tax assets	(208)	59
Unrecognized deferred income tax assets	$ (157)	$ (361)

The amounts of income taxes recoverable in future periods in respect of: (a) deductible temporary differences; (b) the carryforward of unused tax losses; and (c) the carryforward of unused tax credits. [Refer: Temporary differences [member]; Unused tax credits [member]; Unused tax losses [member]]

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The amount of deferred tax liabilities or assets. [Refer: Deferred tax liabilities; Deferred tax assets]

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+ References

No definition available.

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The amount of deferred tax liabilities net of deferred tax assets, when the absolute amount of deferred tax liabilities is greater than the absolute amount of deferred tax assets. [Refer: Deferred tax assets; Deferred tax liabilities]

+ References

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