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Financial Instruments - Estimated Fair Values of Derivative Financial Instruments Included in Risk Management Asset (Details) - CAD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Reconciliation Of Changes In Derivative Financial Assets (Liabilities), Net [Roll Forward] |  |  |
Derivative financial asset (liability), net | $ 356 | $ 101 |
Net change in fair value of outstanding derivatives financial instruments recognized in: Risk management activities | (13) | 35 | $ (37)
Net change in fair value of outstanding derivatives financial instruments recognized in: Foreign exchange | (231) | 260 |
Net change in fair value of outstanding derivatives financial instruments recognized in: Other comprehensive income (loss) | 66 | (40) |
Derivative financial asset (liability), net | 178 | 356 | $ 101
Asset (liability), included in current portion of other long-term (liabilities) assets | (104) | 75 |
Asset (liability), included in other long-term assets | $ 282 | $ 281 |

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- Definition Current Derivative Financial Assets (Liabilities) + References No definition available. + Details
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- Definition Derivative Financial Assets (Liabilities), Net + References No definition available. + Details
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- Definition Gain (Losses) On Change In Fair Value Of Unsettled Derivatives + References No definition available. + Details
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- Definition Gains (Losses) On Exchange Differences On Translation Recognised In Profit Or Loss, Settled And Unsettled Derivative Hedging Instruments + References No definition available. + Details
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- Definition Non-Current Derivative Financial Assets (Liabilities) + References No definition available. + Details
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- Definition Reconciliation Of Changes In Derivative Financial Assets (Liabilities), Net [Roll Forward] + References No definition available. + Details
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- Definition The gains (losses) recognised in other comprehensive income on cash flow hedges, before tax. [Refer: Cash flow hedges [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2019-01-01 -Paragraph 91 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_91_b&doctype=Standard -URIDate 2019-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Note Expiry date 2021-01-01 -Name IFRS -Number 7 -IssueDate 2019-01-01 -Paragraph 23 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2017-en-b&anchor=para_23_c&doctype=Standard&book=b -URIDate 2019-03-27 + Details
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