The applicable income tax rate.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2017-01-01
-Paragraph 81
-Subparagraph c
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_c_ii&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Definition

The amounts of income taxes recoverable in future periods in respect of: (a) deductible temporary differences; (b) the carryforward of unused tax losses; and (c) the carryforward of unused tax credits. [Refer: Temporary differences [member]; Unused tax credits [member]; Unused tax losses [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2017-01-01
-Paragraph 81
-Subparagraph g
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_g_i&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 54
-Subparagraph o
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_54_o&doctype=Standard
-URIDate 2017-03-09

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 56
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_56&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_DeferredTaxAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of tax expense (income) relating to changes in deferred tax liabilities and deferred tax assets. [Refer: Deferred tax assets; Deferred tax liabilities]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2017-01-01
-Paragraph 81
-Subparagraph g
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_g_ii&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Definition

The amounts of income taxes payable in future periods in respect of taxable temporary differences. [Refer: Temporary differences [member]]

+ References

+ Details

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

- Definition

The amount of deferred tax liabilities or assets. [Refer: Deferred tax liabilities; Deferred tax assets]

+ References

+ Details

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

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

+ References

No definition available.

+ Details

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

- Definition

The net loss arising from foreign exchange differences. [Refer: Foreign exchange gain (loss)]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 21
-IssueDate 2017-01-01
-Paragraph 52
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=21&date=2017-03-01&anchor=para_52_a&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Definition

The number of years over which the change in the income tax rate will be enacted.

+ References

No definition available.

+ Details

Name:	su_EffectiveIncomeTaxRateChangeInEnactedTaxRateDuration
Namespace Prefix:	su_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pre-tax income (loss) from continuing operations attributable to changes in the income tax rates.

+ References

No definition available.

+ Details

Name:	su_EffectiveIncomeTaxRateChangeInEnactedTaxRatePercent
Namespace Prefix:	su_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=ifrs-full_UnusedTaxLossesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=su_RetainedEarningsInvestmentsInForeignSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=su_EnactedChangeInCorporateIncomeTaxRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=su_GovernmentOfQuebecMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_GeographicalAreasAxis=su_UnitedKingdomGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=su_UnitedStatesGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=su_GovernmentOfBritishColumbiaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Income Taxes - Deferred Income Tax Asset (Details) - CAD CAD in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Deferred income tax assets	CAD 100.0	CAD 63.0			CAD 100.0	CAD 63.0
Capital losses on foreign exchange					556.0	926.0
Deferred income tax liabilities	11,533.0	11,243.0			11,533.0	11,243.0
Deferred income tax liability (asset)	11,433.0	11,180.0			CAD 11,433.0	CAD 11,180.0	CAD 9,919.0
Tax rate					27.01%	27.00%
Tax loss carryforwards
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Deferred income tax assets	75.0	125.0			CAD 75.0	CAD 125.0
Earnings retained in our investments in foreign subsidiaries
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Deferred income tax liabilities	CAD 9,600.0	CAD 9,900.0			CAD 9,600.0	CAD 9,900.0
Change in corporate income tax rate \| Government Of Quebec
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax rate		11.90%
Enacted tax rate		11.50%
Term in which the enacted tax rate will be in effect		4 years
Deferred income tax expense (recovery)		CAD 10.0
Change in corporate income tax rate \| Government of U.K.
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax rate			50.00%
Enacted tax rate			40.00%
Deferred income tax expense (recovery)			CAD 180.0
United States Government
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax rate					35.00%
Deferred income tax expense (recovery)					CAD (124.0)
United States Government \| Scenario, Forecast [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax rate				21.00%
Government of British Columbia
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]
Tax rate	11.00%
Enacted tax rate	12.00%
Deferred income tax expense (recovery)	CAD 18.0