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Pension and other PostRetirement Benefits (Details) CAD in Millions | 12 Months Ended
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Dec. 31, 2017 CAD Y | Dec. 31, 2016 CAD Y
Minimum |  |
Pension and other PostRetirement Benefits, |  |
Annual contribution (as a percent) | 5.00% |
Maximum |  |
Pension and other PostRetirement Benefits, |  |
Annual contribution (as a percent) | 11.50% |
Defined benefits pension plans |  |
Change in benefit obligation |  |
Disposal (note 36) | CAD (69) |
Actuarial losses (gains) arising from experience adjustments, net defined benefit liability (asset) | (2) | CAD (7)
Defined benefits pension plans | Obligations |  |
Change in benefit obligation |  |
Benefit obligation at beginning of year | 6,280 | 4,611
Obligations acquired through acquisition of COS (note 7) |  | 1,352
Current service costs | 193 | 189
Contributions to plan by plan participants, net defined benefit liability (asset) | 14 | 14
Payments from plan, net defined benefit liability (asset) | (294) | (272)
Interest costs | 236 | 238
Foreign exchange | (2) | (46)
Payments in respect of settlements, net defined benefit liability (asset) | 7 | 8
Actuarial losses (gains) arising from experience adjustments, net defined benefit liability (asset) | 2 | 7
Actuarial losses (gains) arising from changes in demographic assumptions, net defined benefit liability (asset) | (4) | 8
Actuarial losses (gains) arising from changes in financial assumptions, net defined benefit liability (asset) | 354 | 171
Benefit obligation at end of year | 6,717 | 6,280
Defined benefits pension plans | Plan assets |  |
Change in benefit obligation |  |
Benefit obligation at beginning of year | (5,356) | (4,040)
Obligations acquired through acquisition of COS (note 7) |  | (1,060)
Employer contributions | 160 | 165
Contributions to plan by plan participants, net defined benefit liability (asset) | (14) | (14)
Payments from plan, net defined benefit liability (asset) | 269 | 249
Disposal (note 36) | 71 |
Interest costs | (200) | (202)
Foreign exchange | 3 | 37
Payments in respect of settlements, net defined benefit liability (asset) | (7) | (8)
Administrative costs | 2 | 2
Return on plan assets greater than discount rate | 407 | 155
Benefit obligation at end of year | (5,799) | (5,356)
Net unfunded obligation | (918) | (924)
Defined benefits other post retirement benefits |  |
Change in benefit obligation |  |
Disposal (note 36) | (9) |
Actuarial losses (gains) arising from experience adjustments, net defined benefit liability (asset) | 12 | 5
Defined benefits other post retirement benefits | Obligations |  |
Change in benefit obligation |  |
Benefit obligation at beginning of year | 587 | 502
Obligations acquired through acquisition of COS (note 7) |  | 73
Current service costs | 14 | 13
Payments from plan, net defined benefit liability (asset) | (21) | (21)
Interest costs | 22 | 23
Foreign exchange | (1) | (1)
Actuarial losses (gains) arising from experience adjustments, net defined benefit liability (asset) | (12) | (5)
Actuarial losses (gains) arising from changes in demographic assumptions, net defined benefit liability (asset) | (9) | (1)
Actuarial losses (gains) arising from changes in financial assumptions, net defined benefit liability (asset) | 26 | 4
Benefit obligation at end of year | 597 | 587
Defined benefits other post retirement benefits | Plan assets |  |
Change in benefit obligation |  |
Net unfunded obligation | CAD (597) | CAD (587)
Canadian pension and other post retirement benefit excluding Syncrude |  |
Change in benefit obligation |  |
Percentage of net unfunded obligations | 67.00% | 66.00%
Canadian pension and other post retirement benefit excluding Syncrude | Weighted average |  |
Change in benefit obligation |  |
Weighted average duration of defined benefit obligation | Y | 13.91 | 14.06

X
- Definition The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in demographic assumptions that result in remeasurements of the net defined benefit liability (asset). Demographic assumptions deal with matters such as: (a) mortality; (b) rates of employee turnover, disability and early retirement; (c) the proportion of plan members with dependants who will be eligible for benefits; (d) the proportion of plan members who will select each form of payment option available under the plan terms; and (e) claim rates under medical plans. [Refer: Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 141 -Subparagraph c -Clause ii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_c_ii&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions that result in remeasurements of the net defined benefit liability (asset). Financial assumptions deal with items such as: (a) the discount rate; (b) benefit levels, excluding any cost of the benefits to be met by employees, and future salary; (c) in the case of medical benefits, future medical costs, including claim handling costs (ie the costs that will be incurred in processing and resolving claims, including legal and adjuster's fees); and (d) taxes payable by the plan on contributions relating to service before the reporting date or on benefits resulting from that service. [Refer: Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 141 -Subparagraph c -Clause iii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_c_iii&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from experience adjustments that result in remeasurements of the net defined benefit liability (asset). Experience adjustments deal with the effects of differences between the previous actuarial assumptions and what has actually occurred. [Refer: Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 141 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_c&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The decrease (increase) in net defined benefit liability (asset) resulting from contributions to a defined benefit plan by the employer. [Refer: Net defined benefit liability (asset); Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 141 -Subparagraph f -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_f&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The decrease (increase) in the net defined benefit liability (asset) resulting from contributions to a defined benefit plan by plan participants. [Refer: Net defined benefit liability (asset); Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 141 -Subparagraph f -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_f&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The increase (decrease) in the net defined benefit liability (asset) resulting from employee service in the current period. [Refer: Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 141 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_a&doctype=Standard -URIDate 2017-03-09 + 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 2017-01-01 -Paragraph 141 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_e&doctype=Standard -URIDate 2017-03-09 + 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 2017-01-01 -Paragraph 141 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_b&doctype=Standard -URIDate 2017-03-09 + 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 2017-01-01 -Paragraph 140 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_140_a&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan. [Refer: Net defined benefit liability (asset)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 141 -Subparagraph g -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_g&doctype=Standard -URIDate 2017-03-09 + 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: Gains (losses) arising from settlements, net defined benefit liability (asset); Net defined benefit liability (asset); Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 141 -Subparagraph g -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_g&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The present value of the defined benefit obligation, less the fair value of the plan assets (if any). [Refer: Plan assets [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 57 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_57_a&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The weighted average duration of a defined benefit obligation. [Refer: Weighted average [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 147 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_147_c&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The effect on the net defined benefit liability (asset) of expenses related to defined benefit plans that the entity classifies as being administrative. + References No definition available. + Details
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- Definition The increase (decrease) in the net defined benefit liability (asset) resulting from business combinations. + References No definition available. + Details
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- Definition The increase (decrease) in the net defined benefit liability (asset) resulting from disposals. + References No definition available. + Details
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- Definition The percentage of net unfunded obligation. + References No definition available. + Details
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- Definition Return on plan assets greater than discount rate. + References No definition available. + Details
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- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
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