Cash Flow Information (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of cash flow statement [Abstract]
Accounts receivable	$ (79)	$ 261	$ 58
Prepaid expenses	2	0	19
Income taxes receivable	(4)	(6)	0
Inventory	6	(13)	(21)
Accounts payable, accrued liabilities and provisions	160	(130)	(97)
Income taxes payable	4	9	(3)
Change in non-cash operating working capital	$ 89	$ 121	$ (44)

Adjustments for decrease (increase) in trade accounts receivable to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2019-01-01
-Paragraph 20
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=7&code=ifrs-tx-2019-en-r&anchor=para_20_a&doctype=Standard
-URIDate 2019-03-27

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration