FINANCIAL RISK MANAGEMENT - Foreign Exchange Risk (Details) $ in Thousands, $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)	Dec. 31, 2017 CAD ($)	Dec. 31, 2016 CAD ($)
Disclosure of nature and extent of risks arising from financial instruments [line items]
Change in foreign exchange rate	0.01	0.01
Foreign exchange gain (loss)		$ 17,501	$ 8,195
Foreign Exchange Risk
Disclosure of nature and extent of risks arising from financial instruments [line items]
Percentage of anticipated commodity transaction exposures that are hedged	60.00%	60.00%
Foreign exchange gain (loss)	$ 0.8

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
-Number 7
-IssueDate 2017-01-01
-Section A Statement of cash flows for an entity other than a financial institution
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2017-03-01&anchor=sect_AStatementofcashflowsforanentityotherthanafinancialinstitution&doctype=Illustrative%20Examples
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 21
-IssueDate 2017-01-01
-Paragraph 52
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=21&date=2017-03-01&anchor=para_52_a&doctype=Standard
-URIDate 2017-03-09

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration