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Financial Instruments - Summary of Changes in the Fair Value of Cenovus's Risk Management Assets and Liabilities (Detail) - CAD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Reconciliation Of Changes In Fair Value Measurement Assets Liabilities [Abstract] |  |
Fair Value of Contracts, Beginning of Year | $ 3 | $ 160
Fair Value of Contracts Realized During the Year | 252 | 7
Change in Fair Value of Contracts in Place at Beginning of Year and Contracts Entered Into During the Year | (308) | (156)
Unrealized Foreign Exchange Gain (Loss) on U.S. Dollar Contracts |  | (8)
Fair Value of Contracts, End of Year | $ (53) | $ 3

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- Definition Change in fair value of derivative financial instruments from foreign exchange. + References No definition available. + Details
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- Definition Fair value of derivative financial instruments asset (liability) net. + References No definition available. + Details
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Namespace Prefix: | cve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Gains losses on change in fair value of contracts. + References No definition available. + Details
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- Definition Reconciliation Of Changes In Fair Value Measurement Assets Liabilities [Abstract] + References No definition available. + Details
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- Definition Settlements fair value measurement assets liabilities including discontinued operations. + References No definition available. + Details
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Namespace Prefix: | cve_
Data Type: | xbrli:monetaryItemType
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