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Summary of Realized and Unrealized Gain or (Loss) on Derivative Instruments (Detail) - CAD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Financial Instruments And Derivatives [Line Items] |  |  |
Revenues | $ (3) | $ 6 |
Purchases of crude oil and products | (7) | (24) | (5)
Total | $ (10) | $ (18) | $ (5)

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- Definition Financial Instruments And Derivatives [Line Items] + References No definition available. + Details
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- Definition Total realized and unrealized purchase on derivative instrument. + References No definition available. + Details
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- Definition Total realized and unrealized revenue on derivative instrument. + References No definition available. + Details
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- Definition Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959 + Details
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