Decommissioning Liabilities - Summary of Decommissioning Provision (Detail) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Provision for decommissioning, restoration and rehabilitation costs [abstract]
Beginning balance	$ 1,248	$ 1,235
Acquisitions (Note 5)	2,856	0
Liabilities Incurred	30	14
Liabilities Settled	(144)	(42)
Liabilities Disposed	(140)	(2)
Transfers to Liabilities Related to Assets Held for Sale (Note 16)	(128)	0
Change in Estimated Future Cash Flows	(472)	13
Change in Discount Rates	450	(28)
Unwinding of Discount on Decommissioning Liabilities (Note 7)	199	57
Foreign Currency Translation	7	1
Ending balance	$ 3,906	$ 1,248

Acquisitions through business combinations, decommissioning liabilities

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Increase (Decrease) In Existing Provision, Other Provisions

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Increase (decrease) through transfers, assets held-for-sale

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The increase (decrease) in other provisions resulting from a change in discount rate. [Refer: Other provisions]

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The increase (decrease) in other provisions resulting from foreign currency exchange rate changes on provisions measured in a currency different from the entity's presentation currency. [Refer: Other provisions]

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The increase in other provisions through adjustments arising from the passage of time. [Refer: Other provisions]

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The increase (decrease) in other provisions resulting from transfers and changes that the entity does not separately disclose in the same statement or note. [Refer: Other provisions]

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The amount recognised for new other provisions. [Refer: Other provisions]

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The amount of provision for costs related to decommissioning, restoration and rehabilitation. [Refer: Other provisions]

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The amount used (ie incurred and charged against the provision) for other provisions. [Refer: Other provisions]

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