Long-Term Debt - Additional Information (Detail) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Disclosure of detailed information about borrowings [Line Items]
Interest paid on long-term debt	$ 222	$ 324
Level 2 [Member]
Disclosure of detailed information about borrowings [Line Items]
Fair value of long-term debt	$ 4,886	$ 5,186

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 2018-01-01
-Paragraph 112
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_112_c&doctype=Standard
-URIDate 2018-03-16

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