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Financial Instruments - Fair Value of the Commodity Risk Management Assets and Liabilities by Classification Level (Details) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Change in foreign exchange rates | $ 5 | $ (7) | $ 4
Losses recognized in other comprehensive loss | (23) | 75 | 126
Total (losses) gains included in earnings before income taxes | 270 | 51 | (694)
Level III | Recurring fair value measurement |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Commodity risk management assets and liabilities | (153) | (147) | (782)
Market price changes | 23 | 525 |
Change in foreign exchange rates | (10) | 16 |
Transfers out of Level III(2) | 0 | 205 |
Level III | Recurring fair value measurement | Heartland acqusition |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 3 | 0 |
Level III | Recurring fair value measurement | Market price changes on existing contracts |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | (49) | (129) |
Level III | Recurring fair value measurement | Market price changes on new contracts |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 27 | 18 |
Level III | Non-recurring fair value measurement |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Losses recognized in other comprehensive loss | 0 | (114) |
Total (losses) gains included in earnings before income taxes | (32) | (237) |
Unrealized (losses) gains included in earnings before income taxes relating to net assets (liabilities) held at year end | (9) | 288 |
Level III | Hedge | Recurring fair value measurement |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Commodity risk management assets and liabilities | 0 | 0 | (347)
Market price changes | 0 | 256 |
Change in foreign exchange rates | 0 | 9 |
Transfers out of Level III(2) | 0 | 205 |
Level III | Hedge | Recurring fair value measurement | Heartland acqusition |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 0 | 0 |
Level III | Hedge | Recurring fair value measurement | Market price changes on existing contracts |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 0 | (123) |
Level III | Hedge | Recurring fair value measurement | Market price changes on new contracts |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 0 | 0 |
Level III | Hedge | Non-recurring fair value measurement |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Losses recognized in other comprehensive loss | 0 | (114) |
Total (losses) gains included in earnings before income taxes | 0 | (256) |
Unrealized (losses) gains included in earnings before income taxes relating to net assets (liabilities) held at year end | 0 | 0 |
Level III | Non-hedge | Recurring fair value measurement |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Commodity risk management assets and liabilities | (153) | (147) | $ (435)
Market price changes | 23 | 269 |
Change in foreign exchange rates | (10) | 7 |
Transfers out of Level III(2) | 0 | 0 |
Level III | Non-hedge | Recurring fair value measurement | Heartland acqusition |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 3 | 0 |
Level III | Non-hedge | Recurring fair value measurement | Market price changes on existing contracts |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | (49) | (6) |
Level III | Non-hedge | Recurring fair value measurement | Market price changes on new contracts |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Market price changes | 27 | 18 |
Level III | Non-hedge | Non-recurring fair value measurement |  |  |
Disclosure of risk management strategy related to hedge accounting [line items] |  |  |
Losses recognized in other comprehensive loss | 0 | 0 |
Total (losses) gains included in earnings before income taxes | (32) | 19 |
Unrealized (losses) gains included in earnings before income taxes relating to net assets (liabilities) held at year end | $ (9) | $ 288 |

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- 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 2024-01-01 -Paragraph 24C -Subparagraph a -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2024-en-r&anchor=para_24C_a_i&doctype=Standard -URIDate 2024-03-27 + Details
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- 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]; Classes of financial instruments [domain]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 21 -IssueDate 2024-01-01 -Paragraph 52 -Subparagraph a -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=21&code=ifrs-tx-2024-en-r&anchor=para_52_a&doctype=Standard -URIDate 2024-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2024-01-01 -Paragraph 35 -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_35&doctype=Standard -URIDate 2024-03-27 + Details
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