Capital Management - Summary of Capitalization and Ratio (Detail) - CAD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Capitalisation [Abstract]
Long-term debt	$ 1,730,437	$ 1,906,934
Shareholders’ equity	1,810,336	1,962,118
Total capitalization	$ 3,540,773	$ 3,869,052
Long-term debt to long-term debt plus equity ratio	0.49%	0.49%

The amount of equity attributable to the owners of the parent. This specifically excludes non-controlling interest.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2016-01-13
-Paragraph 54
-Subparagraph r
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_54_r&doctype=Standard
-URIDate 2016-03-31

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