Income Taxes - Summary of Deferred Tax Assets and Liabilities (Detail) - CAD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets and liabilities [abstract]
Deferred tax assets	$ 4,318	$ 4,569
Deferred tax liabilities	(1,814)	(1,281)
Net deferred tax assets (liabilities)	$ 2,504	$ 3,288	$ 3,080

The amounts of income taxes recoverable in future periods in respect of: (a) deductible temporary differences; (b) the carryforward of unused tax losses; and (c) the carryforward of unused tax credits. [Refer: Temporary differences [member]; Unused tax credits [member]; Unused tax losses [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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