Cash Flow Information (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from (used in) operating activities [abstract]
Accounts receivable	$ 261	$ 58	$ (228)
Prepaid expenses	0	19	(75)
Income taxes receivable	(6)	0	8
Inventory	(13)	(21)	(7)
Accounts payable, accrued liabilities and provisions	(130)	(97)	186
Income taxes payable	9	(3)	2
Increase (decrease) in working capital	$ 121	$ (44)	$ (114)

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 2018-01-01
-Paragraph 20
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2018-03-01&anchor=para_20_a&doctype=Standard
-URIDate 2018-03-16

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