Long-Term Debt - Additional Information (Detail) - CAD CAD in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about borrowings [Line Items]
Interest paid on long-term debt	CAD 324	CAD 191
Level 2 [Member]
Disclosure of detailed information about borrowings [Line Items]
Fair value of long-term debt	CAD 5,187	CAD 6,100

The amount of interest expense on borrowings. [Refer: Interest expense; Borrowings]

Reference 1: 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

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