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Employee Future Benefits - Fair Value of Plan Assets (Details) $ in Millions, $ in Millions | 12 Months Ended
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Dec. 31, 2024 CAD ($) | Dec. 31, 2023 CAD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 CAD ($)
Disclosure of net defined benefit liability (asset) [line items] |  |  |  |
Net asset, beginning of period | $ (162) |  |  |
Administration expenses | (1) | $ (1) |  | $ (1)
Net asset, ending of period | (154) | (162) |  |
Voluntary contribution | 0 | 4 | $ 3 |
Plan assets |  |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |  |
Net asset, beginning of period | 284 | 289 |  |
Interest on plan assets | 13 | 14 |  |
Net return on plan assets | 12 | 14 |  |
Contributions | 8 | 13 |  |
Benefits paid | (37) | (44) |  |
Administration expenses | (1) | (1) |  |
Effect of settlement from annuitization of the U.S. defined benefit plan (Note 27) | (23) |  |  |
Change in foreign exchange rates | 1 | (1) |  |
Net asset, ending of period | 257 | 284 |  | 289
Registered |  |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |  |
Net asset, beginning of period | (71) |  |  |
Administration expenses | (1) | (1) |  | (1)
Net asset, ending of period | (62) | (71) |  |
Registered | Plan assets |  |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |  |
Net asset, beginning of period | 269 | 274 |  |
Interest on plan assets | 12 | 13 |  |
Net return on plan assets | 13 | 15 |  |
Contributions | 1 | 5 |  |
Benefits paid | (31) | (36) |  |
Administration expenses | (1) | (1) |  |
Effect of settlement from annuitization of the U.S. defined benefit plan (Note 27) | (23) |  |  |
Change in foreign exchange rates | 1 | (1) |  |
Net asset, ending of period | 241 | 269 |  | 274
Supplemental |  |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |  |
Net asset, beginning of period | (74) |  |  |
Administration expenses | 0 | 0 |  | 0
Net asset, ending of period | (74) | (74) |  |
Supplemental | Plan assets |  |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |  |
Net asset, beginning of period | 15 | 15 |  |
Interest on plan assets | 1 | 1 |  |
Net return on plan assets | (1) | (1) |  |
Contributions | 6 | 6 |  |
Benefits paid | (5) | (6) |  |
Administration expenses | 0 | 0 |  |
Effect of settlement from annuitization of the U.S. defined benefit plan (Note 27) | 0 |  |  |
Change in foreign exchange rates | 0 | 0 |  |
Net asset, ending of period | 16 | 15 |  | 15
Other |  |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |  |
Net asset, beginning of period | (17) |  |  |
Administration expenses | 0 | 0 |  | 0
Net asset, ending of period | (18) | (17) |  |
Other | Plan assets |  |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |  |
Net asset, beginning of period | 0 | 0 |  |
Interest on plan assets | 0 | 0 |  |
Net return on plan assets | 0 | 0 |  |
Contributions | 1 | 2 |  |
Benefits paid | (1) | (2) |  |
Administration expenses | 0 | 0 |  |
Effect of settlement from annuitization of the U.S. defined benefit plan (Note 27) | 0 |  |  |
Change in foreign exchange rates | 0 | 0 |  |
Net asset, ending of period | $ 0 | $ 0 |  | $ 0

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- Definition The decrease (increase) in the net defined benefit liability (asset) resulting from contributions to a defined benefit plan. [Refer: Net defined benefit liability (asset); Defined benefit plans [domain]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 141 -Subparagraph f -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_141_f&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table. + References No definition available. + Details
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- Definition The decrease (increase) in the net defined benefit liability (asset) resulting from settlements. Settlements are transactions that eliminate all further legal or constructive obligations for part or all of the benefits provided under a defined benefit plan, other than a payment of benefits to, or on behalf of, employees that is set out in the terms of the plan and included in the actuarial assumptions. [Refer: Net defined benefit liability (asset); Defined benefit plans [domain]; Actuarial assumptions [domain]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 141 -Subparagraph d -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_141_d&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition The increase (decrease) in the net defined benefit liability (asset) resulting from changes in foreign exchange rates. [Refer: Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 141 -Subparagraph e -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_141_e&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition The increase (decrease) in the net defined benefit liability (asset) resulting from the passage of time. [Refer: Interest expense; Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 141 -Subparagraph b -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_141_b&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [domain]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 140 -Subparagraph a -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_140_a&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan in respect of settlements. [Refer: Decrease (increase) in net defined benefit liability (asset) resulting from gains (losses) arising from settlements; Net defined benefit liability (asset); Defined benefit plans [domain]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 141 -Subparagraph g -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_141_g&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition The decrease (increase) in the net defined benefit liability (asset) resulting from the return on plan assets, excluding amounts included in interest income or expense. The return on plan assets is interest, dividends and other revenue derived from the plan assets, together with realised and unrealised gains or losses on the plan assets, less any costs of managing plan assets and less any tax payable by the plan itself, other than tax included in the actuarial assumptions used to measure the present value of the defined benefit obligation. [Refer: Plan assets [member]; Net defined benefit liability (asset); Actuarial assumptions [domain]; Increase (decrease) in net defined benefit liability (asset) resulting from interest expense (income)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 141 -Subparagraph c -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_141_c_i&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition Administrative Expenses, Net Defined Benefit Liability (Asset) + References No definition available. + Details
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