Income Taxes - Reconciliation of Income Taxes Calculated at Statutory Rate (Detail) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation Of Average Effective Tax Rate And Applicable Tax Rate [Abstract]
Earnings (Loss) From Continuing Operations Before Income Tax	$ (3,230)	$ 1,397	$ (3,926)
Canadian Statutory Rate	24.00%	26.50%	27.00%
Expected Income Tax Expense (Recovery) From Continuing Operations	$ (775)	$ 370	$ (1,060)
Effect on Taxes Resulting From:
Statutory and Other Rate Differences	19	(52)	(57)
Non-Taxable Capital (Gains) Losses	(42)	(38)	89
Non-Recognition of Capital (Gains) Losses	(42)	(39)	87
Adjustments Arising From Prior Year Tax Filings	(8)	4	3
Recognition of U.S. Tax Basis		(387)	(78)
Alberta Corporate Rate Reduction	(7)	(671)
Other	4	16	6
Tax Expense (Recovery) From Continuing Operations	$ (851)	$ (797)	$ (1,010)
Effective Tax Rate	26.30%	(57.10%)	25.70%

Adjustments of tax expense (income) recognized in the period for tax of prior periods.

No definition available.

Name:	cve_AdjustmentsForTaxOfPriorPeriods
Namespace Prefix:	cve_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Deferred tax impact of adjustment to US tax basis.

+ References

No definition available.

+ Details

Name:	cve_DeferredTaxImpactOfAdjustmentToUSTaxBasis
Namespace Prefix:	cve_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Deferred tax impact of Alberta Corporate rate reduction.

+ References

No definition available.

+ Details

Name:	cve_DeferredTaxImpactOfAlbertaCorporateRateReduction
Namespace Prefix:	cve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The non-taxable portion of realized and unrealized capital gains/losses recognized in the period.

+ References

No definition available.

+ Details

Name:	cve_NonTaxablePortionOfRealizedAndUnrealizedCapitalGainsLossesRecognized
Namespace Prefix:	cve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Source of origin of tax rate differential.

+ References

No definition available.

+ Details

Name:	cve_SourceOfOriginOfTaxRateDifferentialAbstract
Namespace Prefix:	cve_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax effect of non-recognition of capital (gains) losses.

+ References

No definition available.

+ Details

Name:	cve_TaxEffectOfNonRecognitionOfCapitalGainsLosses
Namespace Prefix:	cve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of profit (loss) for a period before deducting tax expense. [Refer: Profit (loss)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2020-01-01
-Paragraph 81
-Subparagraph c
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_c_ii&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2020-01-01
-Paragraph 81
-Subparagraph c
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_c_i&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_AccountingProfit
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The applicable income tax rate.

+ References

+ Details

Name:	ifrs-full_ApplicableTaxRate
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The tax expense (income) divided by the accounting profit. [Refer: Accounting profit]

+ References

+ Details

Name:	ifrs-full_AverageEffectiveTaxRate
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate amount included in the determination of profit (loss) for the period in respect of current tax and deferred tax. [Refer: Current tax expense (income); Deferred tax expense (income)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2020-01-01
-Paragraph 23
-Subparagraph h
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2020-en-r&anchor=para_23_h&doctype=Standard
-URIDate 2020-01-01

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 26
-IssueDate 2020-01-01
-Paragraph 35
-Subparagraph b
-Clause viii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=26&code=ifrs-tx-2020-en-r&anchor=para_35_b_viii&doctype=Standard
-URIDate 2020-01-01

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2020-01-01
-Paragraph 79
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_79&doctype=Standard
-URIDate 2020-01-01

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2020-01-01
-Paragraph 81
-Subparagraph c
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_c_i&doctype=Standard
-URIDate 2020-01-01

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2020-01-01
-Paragraph 82
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_82_d&doctype=Standard
-URIDate 2020-01-01

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2020-01-01
-Paragraph 81
-Subparagraph c
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_c_ii&doctype=Standard
-URIDate 2020-01-01

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2020-01-01
-Paragraph B13
-Subparagraph g
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2020-en-r&anchor=para_B13_g&doctype=Appendix&subtype=B
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_IncomeTaxExpenseContinuingOperations
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that the entity does not separately disclose in the same statement or note. [Refer: Accounting profit; Applicable tax rate]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2020-01-01
-Paragraph 81
-Subparagraph c
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2020-en-r&anchor=para_81_c_i&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_OtherTaxEffectsForReconciliationBetweenAccountingProfitAndTaxExpenseIncome
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	ifrs-full_ReconciliationOfAverageEffectiveTaxRateAndApplicableTaxRateAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to changes in the tax rate. [Refer: Accounting profit]

+ References

+ Details

Name:	ifrs-full_TaxEffectFromChangeInTaxRate
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The product of the accounting profit multiplied by the applicable tax rate(s). [Refer: Accounting profit; Applicable tax rate]

+ References

+ Details

Name:	ifrs-full_TaxExpenseIncomeAtApplicableTaxRate
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration