Other Assets (Details) - CAD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
OTHER ASSETS.
Investments	$ 237	$ 224
Prepaids and other	889	987
Other assets	$ 1,126	$ 1,211

The amount of investments in subsidiaries, joint ventures and associates in an entity's separate financial statements. [Refer: Associates [member]; Joint ventures [member]; Subsidiaries [member]; Investments in subsidiaries]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2018-01-01
-Paragraph 10
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2018-03-01&anchor=para_10&doctype=Standard
-URIDate 2018-03-16

+ Details

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

- Definition

The amount of non-current prepayments. [Refer: Prepayments]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 78
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_78_b&doctype=Standard
-URIDate 2018-03-16

+ Details

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

- Definition

The amount of assets that the entity does not separately disclose in the same statement or note.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_55&doctype=Standard
-URIDate 2018-03-16

+ Details

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

- Definition

n/a

+ References

No definition available.

+ Details

Name:	su_OtherAssetsDisclosureAbstract
Namespace Prefix:	su_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration