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Employee future benefits - Actuarial Assumptions (Details) | Dec. 31, 2018 | Dec. 31, 2017
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Pension Plan |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Discount rate, fair value benefit obligation | 4.16% | 3.60%
Discount rate, net expense | 3.60% | 4.13%
Other post-retirement benefit plan |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Discount rate, fair value benefit obligation | 3.96% | 3.27%
Discount rate, net expense | 3.96% | 3.27%
Initial medical/dental health care cost trend rate |  | 8.00%
Other post-retirement benefit plan | Actuarial assumption of medical cost trend rates |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Cost trend rate declines to medical and dental |  | 5.00%

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- Definition Actuarial Assumption Of Medical Cost Trend Rates Declines + References No definition available. + Details
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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 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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