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Financial Instruments - Reconciliation of Changes in the Fair Value of Cenovus's Risk Management Assets and Liabilities (Detail) - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Disclosure of detailed information about financial instruments [abstract]    
Fair Value of Contracts, Beginning of Year $ (53) $ 3
Acquisition (Note 5A) (14) 0
Fair Value of Contracts Realized During the Year 993 252
Change in Fair Value of Contracts in Place at Beginning of Year and Contracts Entered Into During the Year (995) (308)
Unrealized Foreign Exchange Gain (Loss) on U.S. Dollar Contracts 1 0
Fair Value of Contracts, End of Year $ (68) $ (53)