Decommissioning Liabilities - Summary of Decommissioning Provision (Detail) $ in Millions	6 Months Ended
Jun. 30, 2018 CAD ($)
Provision For Decommissioning Restoration And Rehabilitation Costs [Abstract]
Beginning balance	$ 1,029
Liabilities Incurred	7
Liabilities Settled	(20)
Liabilities Disposed	(1)
Transfers to Liabilities Related to Assets Held for Sale	(2)
Change in Discount Rate	(14)
Unwinding of Discount on Decommissioning Liabilities	31
Foreign Currency Translation	1
Ending balance	$ 1,031

Increase decrease through foreign currency translation.

No definition available.

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

- Definition

The decrease in other provisions resulting from the transfer of those provisions to liabilities included in disposal groups classified as held for sale. [Refer: Other provisions; Disposal groups classified as held for sale [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Paragraph 84
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=para_84&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Paragraph 84
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=para_84_e&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Definition

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

+ References

+ Details

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

- Definition

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]

+ References

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Paragraph 84
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=para_84_b&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Section D Examples: disclosures
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=sect_DExamples:disclosures&doctype=Illustrative%20Examples
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Paragraph 87
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=para_87&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_ProvisionForDecommissioningRestorationAndRehabilitationCosts
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Paragraph 84
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=para_84_c&doctype=Standard
-URIDate 2017-03-09

+ Details

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