Foreign Exchange (Gain) Loss, Net - Schedule of Foreign Exchange Gain Loss Net (Detail) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Foreign Exchange Gains Losses:
Unrealized Foreign Exchange (Gain) Loss	$ (131)	$ (827)	$ 649
Realized Foreign Exchange (Gain) Loss	(50)	423	205
Total	(181)	(404)	854
Long-term Borrowings [Member]
Foreign Exchange Gains Losses:
Unrealized Foreign Exchange (Gain) Loss	(194)	(800)	602
Other [Member]
Foreign Exchange Gains Losses:
Unrealized Foreign Exchange (Gain) Loss	$ 63	$ (27)	$ 47

The amount of exchange differences recognised in profit or loss that arise from foreign currency transactions, excluding those arising on financial instruments measured at fair value through profit or loss in accordance with IFRS 9. [Refer: At fair value [member]; Financial instruments, class [member]]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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