XML 136 R108.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Income Taxes - Significant Components of Deferred Income Tax Assets (Liabilities) (Details) - CAD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Writedown of deferred income tax assets | $ (28) | $ (24)
Net deferred tax liabilities | (473) | (525)
Gross carrying amount | Net operating loss carryforwards |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deferred tax liability (asset) | 547 | 541
Gross carrying amount | Future decommissioning and restoration costs |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deferred tax liability (asset) | 113 | 117
Gross carrying amount | Property, plant and equipment |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deferred tax liability (asset) | (896) | (1,009)
Gross carrying amount | Risk management assets and liabilities, net |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deferred tax liability (asset) | (145) | (160)
Gross carrying amount | Employee future benefits and compensation plans |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deferred tax liability (asset) | 68 | 74
Gross carrying amount | Interest deductible in future periods |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deferred tax liability (asset) | 48 | 50
Gross carrying amount | Foreign exchange differences on US-denominated debt |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deferred tax liability (asset) | 35 | 42
Gross carrying amount | Deferred coal revenues |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deferred tax liability (asset) | 23 | 16
Gross carrying amount | Other deductible temporary differences |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deferred tax liability (asset) | 0 | 22
Accumulated impairment |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Deferred tax liability (asset) | (207) | (307)
Writedown of deferred income tax assets | 266 | 218
Net deferred tax liabilities | $ (473) | $ (525)

X
- Definition The amounts of income taxes recoverable in future periods in respect of: (a) deductible temporary differences; (b) the carryforward of unused tax losses; and (c) the carryforward of unused tax credits. [Refer: Temporary differences [member]; Unused tax credits [member]; Unused tax losses [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2017-01-01 -Paragraph 81 -Subparagraph g -Clause i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_g_i&doctype=Standard -URIDate 2017-03-09 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 54 -Subparagraph o -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_54_o&doctype=Standard -URIDate 2017-03-09 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 56 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_56&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_DeferredTaxAssets
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of deferred tax liabilities or assets. [Refer: Deferred tax liabilities; Deferred tax assets] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2017-01-01 -Paragraph 81 -Subparagraph g -Clause i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_g_i&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_DeferredTaxLiabilityAsset
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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_DisclosureOfTemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of deferred tax liabilities net of deferred tax assets, when the absolute amount of deferred tax liabilities is greater than the absolute amount of deferred tax assets. [Refer: Deferred tax assets; Deferred tax liabilities] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 12 -IssueDate 2017-01-01 -Paragraph 81 -Subparagraph g -Clause i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2017-03-01&anchor=para_81_g_i&doctype=Standard -URIDate 2017-03-09 + Details
Name: | ifrs-full_NetDeferredTaxLiabilities
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | ifrs-full_CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis=ifrs-full_GrossCarryingAmountMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=ifrs-full_UnusedTaxLossesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=tac_DecommissioningRestorationAndRehabilitationCostsRelatedTemporaryDifferencesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=tac_PropertyPlantAndEquipmentRelatedTemporaryDifferencesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=tac_NetRiskManagementAssetsAndLiabilitiesTemporaryDifferencesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=tac_EmployeeBenefitsAndCompensationPlansTemporaryDifferencesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=tac_InterestDeductibleInFuturePeriodsTemporaryDifferencesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=tac_ForeignExchangeTemporaryDifferencesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=tac_DeferredRevenuesTemporaryDifferencesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TemporaryDifferenceUnusedTaxLossesAndUnusedTaxCreditsAxis=ifrs-full_OtherTemporaryDifferencesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis=ifrs-full_AccumulatedImpairmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |