XML 169 R118.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Financial Instruments Fair value of the commodity risk management assets and liabilities by classification level (Details) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Foreign exchange gain (loss) | $ (15) | $ (15) | $ (1)
Gains recognized in other comprehensive income | (53) | (57) | (138)
Gains (losses) on cash flow hedges, before tax | 77 | (9) | 136
Other |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Risk exposure associated with instruments sharing characteristic |  | (2) |
Commodity risk management |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Risk exposure associated with instruments sharing characteristic |  | 679 |
Recurring fair value measurement | Level I |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Risk exposure associated with instruments sharing characteristic | (3) | 3 |
Recurring fair value measurement | Level II |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Risk exposure associated with instruments sharing characteristic | 9 | (19) |
Recurring fair value measurement | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Risk exposure associated with instruments sharing characteristic | 686 | 695 | 771
Market price changes | (76) | (132) |
Foreign exchange gain (loss) | (32) | 72 |
Transfers into Level 3 of fair value hierarchy, assets | 0 | (4) |
Recurring fair value measurement | Level III | Other |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Risk exposure associated with instruments sharing characteristic | 4 | (2) |
Non-recurring fair value measurement [member] | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Gains recognized in other comprehensive income | 46 | 60 |
Gains (losses) on cash flow hedges, before tax | 78 | 90 |
Unrealized gains included in earnings before income taxes relating to met assets held | 2 | (42) |
Fair value hedges [member] | Recurring fair value measurement | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Risk exposure associated with instruments sharing characteristic | 678 | 689 | 719
Market price changes | (57) | (90) |
Foreign exchange gain (loss) | (31) | 67 |
Transfers into Level 3 of fair value hierarchy, assets | 0 | 0 |
Fair value hedges [member] | Non-recurring fair value measurement [member] | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Gains recognized in other comprehensive income | 46 | 60 |
Gains (losses) on cash flow hedges, before tax | 57 | 90 |
Unrealized gains included in earnings before income taxes relating to met assets held | 0 | 0 |
Non-Hedges | Recurring fair value measurement | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Risk exposure associated with instruments sharing characteristic | 8 | 6 | $ 52
Market price changes | (19) | (42) |
Foreign exchange gain (loss) | (1) | 5 |
Transfers into Level 3 of fair value hierarchy, assets | 0 | (4) |
Non-Hedges | Non-recurring fair value measurement [member] | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Gains recognized in other comprehensive income | 0 | 0 |
Gains (losses) on cash flow hedges, before tax | 21 | 0 |
Unrealized gains included in earnings before income taxes relating to met assets held | 2 | (42) |
Derivative Instruments, Existing Contracts [Member] | Recurring fair value measurement | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 85 | (16) |
Derivative Instruments, Existing Contracts [Member] | Fair value hedges [member] | Recurring fair value measurement | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 77 | (7) |
Derivative Instruments, Existing Contracts [Member] | Non-Hedges | Recurring fair value measurement | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 8 | (9) |
Derivative Instruments, New Contracts [Member] | Recurring fair value measurement | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 14 | 4 |
Derivative Instruments, New Contracts [Member] | Fair value hedges [member] | Recurring fair value measurement | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 0 | 0 |
Derivative Instruments, New Contracts [Member] | Non-Hedges | Recurring fair value measurement | Level III |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | $ 14 | $ 4 |

X
- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
Name: | ifrs-full_DisclosureOfRiskManagementStrategyRelatedToHedgeAccountingLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The gain (loss) recognised in other comprehensive income on hedge ineffectiveness. [Refer: Gain (loss) on hedge ineffectiveness] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph 24C -Subparagraph a -Clause i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2018-03-01&anchor=para_24C_a_i&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_GainLossOnHedgeIneffectivenessRecognisedInOtherComprehensiveIncome
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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 2018-01-01 -Paragraph 91 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_91_b&doctype=Standard -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Note Expiry date 2021-01-01 -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph 23 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_23_c&doctype=Standard&book=b -URIDate 2018-03-16 + Details
Name: | ifrs-full_GainsLossesOnCashFlowHedgesBeforeTax
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition 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]] + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Name IAS -Number 7 -IssueDate 2018-01-01 -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=2018-03-01&anchor=sect_AStatementofcashflowsforanentityotherthanafinancialinstitution&doctype=Illustrative%20Examples -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 21 -IssueDate 2018-01-01 -Paragraph 52 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=21&date=2018-03-01&anchor=para_52_a&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_GainsLossesOnExchangeDifferencesOnTranslationRecognisedInProfitOrLoss
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The increase (decrease) in exposure to credit risk on loan commitments and financial guarantee contracts. [Refer: Exposure to credit risk on loan commitments and financial guarantee contracts] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph 35H -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2018-03-01&anchor=para_35H&doctype=Standard -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph 35I -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2018-03-01&anchor=para_35I&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_IncreaseDecreaseInExposureToCreditRiskOnLoanCommitmentsAndFinancialGuaranteeContracts
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The amount of risk exposure associated with financial instruments with a shared characteristic that identifies a concentration of risks. [Refer: Financial instruments, class [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph B8 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2018-03-01&anchor=para_B8_c&doctype=Appendix&seq=2 -URIDate 2018-03-16 + Details
Name: | ifrs-full_RiskExposureAssociatedWithInstrumentsSharingCharacteristic
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount of transfers of assets into Level 3 of the fair value hierarchy. [Refer: Level 3 of fair value hierarchy [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 13 -IssueDate 2018-01-01 -Paragraph 93 -Subparagraph e -Clause iv -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=13&date=2018-03-01&anchor=para_93_e_iv&doctype=Standard -URIDate 2018-03-16 + Details
Name: | ifrs-full_TransfersIntoLevel3OfFairValueHierarchyAssets
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Unrealized Gains (Losses) On Hedge Instruments, Before Tax + References No definition available. + Details
Name: | tac_UnrealizedGainsLossesOnHedgeInstrumentsBeforeTax
Namespace Prefix: | tac_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | ifrs-full_TypesOfRisksAxis=tac_OtherRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfRisksAxis=ifrs-full_CommodityPriceRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_MeasurementAxis=ifrs-full_RecurringFairValueMeasurementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_LevelsOfFairValueHierarchyAxis=ifrs-full_Level1OfFairValueHierarchyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_LevelsOfFairValueHierarchyAxis=ifrs-full_Level2OfFairValueHierarchyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_LevelsOfFairValueHierarchyAxis=ifrs-full_Level3OfFairValueHierarchyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_MeasurementAxis=ifrs-full_NonrecurringFairValueMeasurementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfHedgesAxis=ifrs-full_FairValueHedgesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfHedgesAxis=tac_NonHedgesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfFinancialAssetsAxis=tac_DerivativeInstrumentsExistingContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfFinancialAssetsAxis=tac_DerivativeInstrumentsNewContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |