other operating income (Details) - CAD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
other operating income
Government assistance, including deferral account amortization	$ 6	$ 7	$ 12	$ 14
Investment income, gain on disposal of assets and other	7	7	26	13
Interest income			1
Total	$ 13	$ 14	$ 39	$ 27

The amount of revenue arising from sources that the entity does not separately disclose in the same statement or note. [Refer: Revenue]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2018-01-01
-Name IAS
-Number 18
-IssueDate 2017-01-01
-Paragraph 35
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=18&date=2017-03-02&anchor=para_35_b&doctype=Standard&book=B
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 112
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_112_c&doctype=Standard
-URIDate 2017-03-09

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Data Type:	xbrli:monetaryItemType
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