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Income Taxes - Significant Components of Deferred Income Tax Assets (Liabilities) (Details) - CAD ($) $ in Millions | Dec. 31, 2022 | Dec. 31, 2021
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Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Unrecognized deferred income tax assets | $ (50) | $ (64)
Net deferred income tax liability, after write-down of deferred income tax assets | (302) | (290)
Cost | Non-capital losses |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Net deferred income tax asset, before write-down of deferred income tax assets | 244 | 530
Cost | Future decommissioning and restoration costs |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Net deferred income tax asset, before write-down of deferred income tax assets | 119 | 183
Cost | Property, plant and equipment |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Net deferred income tax asset, before write-down of deferred income tax assets | (553) | (651)
Cost | Risk management assets and liabilities, net |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Net deferred income tax asset, before write-down of deferred income tax assets | 193 | (53)
Cost | Employee future benefits and compensation plans |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Net deferred income tax asset, before write-down of deferred income tax assets | 48 | 53
Cost | Interest deductible in future periods |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Net deferred income tax asset, before write-down of deferred income tax assets | 0 | 17
Cost | Foreign exchange differences on US-denominated debt |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Net deferred income tax asset, before write-down of deferred income tax assets | 13 | 16
Cost | Other deductible temporary differences |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Net deferred income tax asset, before write-down of deferred income tax assets | (5) | (5)
Accumulated impairment |  |
Disclosure of temporary difference, unused tax losses and unused tax credits [line items] |  |
Net deferred income tax asset, before write-down of deferred income tax assets | 59 | 90
Unrecognized deferred income tax assets | $ (361) | $ (380)

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- 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 2022-03-24 -Paragraph 81 -Subparagraph g -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2022-en-r&anchor=para_81_g_i&doctype=Standard -URIDate 2022-03-24 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2022-03-24 -Paragraph 54 -Subparagraph o -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2022-en-r&anchor=para_54_o&doctype=Standard -URIDate 2022-03-24 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2022-03-24 -Paragraph 56 -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2022-en-r&anchor=para_56&doctype=Standard -URIDate 2022-03-24 + Details
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- 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 2022-03-24 -Paragraph 81 -Subparagraph g -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2022-en-r&anchor=para_81_g_i&doctype=Standard -URIDate 2022-03-24 + Details
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- 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 2022-03-24 -Paragraph 81 -Subparagraph g -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2022-en-r&anchor=para_81_g_i&doctype=Standard -URIDate 2022-03-24 + Details
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