Income Taxes - Components of Income Tax Expense (Recovery) Recognized in Other Comprehensive Income ("OCI") (Detail) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Major components of tax expense (income) [abstract]
Current income tax expense (recovery)	$ 2	$ 116
Deferred income tax expense (recovery)	(148)	320
Total income tax expense (recovery)	$ (146)	$ 436

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 2018-01-01
-Paragraph 81
-Subparagraph ab
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2018-03-01&anchor=para_81_ab&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 90
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_90&doctype=Standard
-URIDate 2018-03-16

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