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Employee Future Benefits - Assumptions (Details) | 12 Months Ended |
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Dec. 31, 2018 | Dec. 31, 2018 age | Dec. 31, 2017
Other, through 2027 |  |  |
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) | 4.50% | 4.50% |
Maximum age disabled and retired members eligible for benefits | 65 | 65 |
Percentage of reasonably possible decrease in actuarial assumption | 0.30% | 0.30% |
Other, through 2026 |  |  |
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) | 4.50% | 4.50% | 4.50%
Maximum age disabled and retired members eligible for benefits | 65 |  |
Percentage of reasonably possible decrease in actuarial assumption | 0.30% | 0.30% | 0.30%
Other, through 2026 | US plans |  |  |
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) | 4.50% | 4.50% | 4.50%
Other, through 2024 |  |  |
Assumed health care cost trend rate |  |  |
Maximum age disabled and retired members eligible for benefits | 65 |  |
Other, through 2024 | US plans |  |  |
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) |  |  | 4.50%
Other, through 2024 | Canadian plans |  |  |
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) |  |  | 5.00%
Percentage of reasonably possible decrease in actuarial assumption |  |  | 0.30%
Accrued Benefit Obligation | Registered |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Discount rate | 390000.00% | 390000.00% | 330000.00%
Rate of compensation increase | 250000.00% | 250000.00% | 290000.00%
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) | 0.00% | 0.00% | 0.00%
Dental care cost escalation | 0.00% | 0.00% | 0.00%
Accrued Benefit Obligation | Supplemental |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Discount rate | 380000.00% | 380000.00% | 330000.00%
Rate of compensation increase | 300000.00% | 300000.00% | 300000.00%
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) | 0.00% | 0.00% | 0.00%
Dental care cost escalation | 0.00% | 0.00% | 0.00%
Accrued Benefit Obligation | Other, through 2027 |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Discount rate | 390000.00% | 390000.00% | 340000.00%
Rate of compensation increase | 0.00% | 0.00% | 0.00%
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) | 0.00% | 0.00% | 0.00%
Dental care cost escalation | 400000.00% | 400000.00% | 400000.00%
Other, through 2027 | Registered |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Discount rate | 330000.00% | 330000.00% | 370000.00%
Rate of compensation increase | 260000.00% | 260000.00% | 260000.00%
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) | 0.00% | 0.00% | 0.00%
Dental care cost escalation | 0.00% | 0.00% | 0.00%
Provincial health care premium escalation | 0.00% | 0.00% | 0.00%
Other, through 2027 | Supplemental |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Discount rate | 330000.00% | 330000.00% | 360000.00%
Rate of compensation increase | 300000.00% | 300000.00% | 300000.00%
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) | 0.00% | 0.00% | 0.00%
Dental care cost escalation | 0.00% | 0.00% | 0.00%
Provincial health care premium escalation | 0.00% | 0.00% | 0.00%
Other, through 2027 | Other, through 2027 |  |  |
Disclosure of defined benefit plans [line items] |  |  |
Discount rate | 340000.00% | 340000.00% | 370000.00%
Rate of compensation increase | 0.00% | 0.00% | 0.00%
Assumed health care cost trend rate |  |  |
Health care cost escalation(1)(3) | 0.00% | 0.00% | 0.00%
Dental care cost escalation | 400000.00% | 400000.00% | 400000.00%
Provincial health care premium escalation | 0.00% | 0.00% | 0.00%

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- Definition The discount rate used as the significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit obligation, at present value; Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_144&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The expected rate of inflation that is used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [member]; Defined benefit obligation, at present value; Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_144&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The expected rate of salary increases used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [member]; Defined benefit obligation, at present value; Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_144&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition Medical cost trend rate used as significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit obligation, at present value; Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_144&doctype=Standard -URIDate 2017-03-09 + Details
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- Definition The reasonably possible percentage of the decrease in the actuarial assumption used to determine the present value of defined benefit obligation. [Refer: Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2017-01-01 -Paragraph 145 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_145_a&doctype=Standard -URIDate 2017-03-09 + Details
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