FINANCIAL INSTRUMENTS AND RISK MANAGEMENT - Change in Fair Value (Details) - CAD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in fair value
Total Gain/(Loss)	$ (81,733)	$ 124,266	$ 6,184
Equity Swaps \| General and Administrative
Change in fair value
Total Gain/(Loss)	(308)	210	(184)
Electricity Swaps \| Operating Expense
Change in fair value
Total Gain/(Loss)			639
Commodity Derivative Instruments
Change in fair value
Unrealized Gain (Loss) on Commodity Contracts	(81,425)	124,056	5,729
Commodity Derivative Instruments \| Crude oil \| Commodity derivative instruments
Change in fair value
Unrealized Gain (Loss) on Commodity Contracts	(70,481)	114,822	(5,445)
Commodity Derivative Instruments \| Gas \| Commodity derivative instruments
Change in fair value
Unrealized Gain (Loss) on Commodity Contracts	$ (10,944)	$ 9,234	$ 11,174

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No definition available.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of open agreements to purchase or sell mineral resources, energy, and agricultural products at some future point held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

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