Cash Flow Information (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from (used in) operating activities [abstract]
Accounts receivable	$ 58	$ (228)	$ (23)
Prepaid expenses	19	(75)	5
Income taxes receivable	0	8	(4)
Inventory	(21)	(7)	11
Accounts payable, accrued liabilities, and provisions	(97)	186	81
Income taxes payable	(3)	2	3
Change in non-cash operating working capital	$ (44)	$ (114)	$ 73

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 2017-01-01
-Paragraph 20
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2017-03-01&anchor=para_20_a&doctype=Standard
-URIDate 2017-03-09

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