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Employee Future Benefits - Status of Plans (Details) - CAD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
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Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | $ (162) | $ (158) |
Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (7) | (8) |
Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (155) | (150) |
Fair value of plan assets |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | 284 | 289 | $ 353
Present value of defined benefit obligation |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (446) | (447) |
Registered |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (71) | (71) |
Registered | Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (1) | (1) |
Registered | Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (70) | (70) |
Registered | Fair value of plan assets |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | 269 | 274 | 339
Registered | Present value of defined benefit obligation |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (340) | (345) | (469)
Supplemental |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (74) | (70) |
Supplemental | Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (5) | (6) |
Supplemental | Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (69) | (64) |
Supplemental | Fair value of plan assets |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | 15 | 15 | 14
Supplemental | Present value of defined benefit obligation |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (89) | (85) | (101)
Other |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (17) | (17) |
Other | Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (1) | (1) |
Other | Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (16) | (16) |
Other | Fair value of plan assets |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | 0 | 0 | 0
Other | Present value of defined benefit obligation |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | $ (17) | $ (17) | $ (23)

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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 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 [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2023-01-01 -Paragraph 140 -Subparagraph a -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2023-en-r&anchor=para_140_a&doctype=Standard -URIDate 2023-03-23 + Details
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