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Employee Future Benefits - Status of Plans (Details) - CAD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | --- | ---
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | $ (278) | $ (238) |
Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (10) | (11) |
Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (268) | (227) |
Fair value of plan assets |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | 386 | 381 | $ 428
Present value of defined benefit obligation |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (664) | (619) |
Registered |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (170) | (146) |
Registered | Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (3) | (5) |
Registered | Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (167) | (141) |
Registered | Fair value of plan assets |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | 373 | 368 | 416
Registered | Present value of defined benefit obligation |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (543) | (514) | (561)
Supplemental Pension Plan |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (86) | (67) |
Supplemental Pension Plan | Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (5) | (5) |
Supplemental Pension Plan | Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (81) | (62) |
Supplemental Pension Plan | Fair value of plan assets |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | 13 | 13 | 12
Supplemental Pension Plan | Present value of defined benefit obligation |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (99) | (80) | (87)
Other |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (22) | (25) |
Other | Accrued current liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (2) | (1) |
Other | Other long-term liabilities |  |  |
Disclosure of net defined benefit liability (asset) [line items] |  |  |
Net defined benefit liability (asset) | (20) | (24) |
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) | $ (22) | $ (25) | $ (27)

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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain 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 2018-01-01 -Paragraph 140 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_140_a&doctype=Standard -URIDate 2018-03-16 + Details
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