Employee Future Benefits - Contributions (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 CAD ($)
Registered
Disclosure of defined benefit plans [line items]
Expected employer contributions	$ 4
Supplemental Pension Plan
Disclosure of defined benefit plans [line items]
Expected employer contributions	5
Other
Disclosure of defined benefit plans [line items]
Expected employer contributions	1
Total
Disclosure of defined benefit plans [line items]
Expected employer contributions	$ 10

The estimate of the expected contributions to be made to a defined benefit plan for the next annual reporting period. [Refer: Defined benefit plans [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2018-01-01
-Paragraph 147
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_147_b&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2018-01-01
-Paragraph 148
-Subparagraph d
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_148_d_iii&doctype=Standard
-URIDate 2018-03-16

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