Inventory Change in Inventory (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Disclosure of inventories [Abstract]
Inventories at the beginning of the period	$ 251	$ 242
Net addition		12
Change in foreign exchange rates	(2)	(3)
Writedowns	37
Net addition	26
Inventories at the end of the period	$ 238	$ 251

The amount of current inventories. [Refer: Inventories]

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