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Employee Future Benefits - Status of Plans (Details) - CAD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
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Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | $ (240) | $ (294) |
Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (12) | (12) |
Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (228) | (282) |
Fair value of plan assets |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | 353 | 381 | $ 386
Present value of defined benefit obligation |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (593) | (675) |
Registered |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (130) | (175) |
Registered | Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (4) | (5) |
Registered | Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (126) | (170) |
Registered | Fair value of plan assets |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | 339 | 367 | 373
Registered | Present value of defined benefit obligation |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (469) | (542) | (543)
Supplemental Pension Plan |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (87) | (95) |
Supplemental Pension Plan | Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (6) | (5) |
Supplemental Pension Plan | Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (81) | (90) |
Supplemental Pension Plan | Fair value of plan assets |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | 14 | 14 | 13
Supplemental Pension Plan | Present value of defined benefit obligation |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (101) | (109) | (99)
Other |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (23) | (24) |
Other | Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (2) | (2) |
Other | Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (21) | (22) |
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) | $ (23) | $ (24) | $ (22)

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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 2021-01-01 -Paragraph 140 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2021-en-r&anchor=para_140_a&doctype=Standard -URIDate 2021-03-24 + Details
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