Income Taxes - Components of Income Tax Expense (Recovery) Recognized in Other Comprehensive Income ("OCI") (Detail) - CAD CAD in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Major components of tax expense (income) [abstract]
Current income tax expense (recovery)	CAD 116	CAD (72)
Deferred income tax expense (recovery)	320	(25)
Total income tax expense (recovery)	CAD 436	CAD (97)

The amount of income tax relating to amounts recognised in other comprehensive income. [Refer: Other comprehensive income]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2017-01-01
-Paragraph 81
-Subparagraph ab
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_ab&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 90
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_90&doctype=Standard
-URIDate 2017-03-09

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