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Post-retirement benefits - Summary of main assumptions rate for valuations of plans (Detail) | Dec. 31, 2017 | Dec. 31, 2016
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Canada [member] |  |
Disclosure of defined benefit plans [Line Items] |  |
Discount rate | 3.40% | 3.80%
Inflation | 1.80% | 1.90%
Rate of increase in pensions | 0.50% | 0.40%
Rate of increase in salaries | 3.10% | 3.20%
United Kingdom [member] |  |
Disclosure of defined benefit plans [Line Items] |  |
Discount rate | 2.30% | 2.60%
Inflation | 3.20% | 3.30%
Rate of increase in pensions | 2.80% | 2.90%
Rate of increase in salaries | 3.60% | 3.70%
United States [member] |  |
Disclosure of defined benefit plans [Line Items] |  |
Discount rate | 3.50% | 3.90%
Inflation | 2.10% | 2.10%
Rate of increase in pensions | 0.00% | 0.00%
Rate of increase in salaries | 3.60% | 3.60%
Switzerland [member] |  |
Disclosure of defined benefit plans [Line Items] |  |
Discount rate | 0.50% | 0.60%
Inflation | 1.20% | 1.00%
Rate of increase in pensions | 0.40% | 0.00%
Rate of increase in salaries | 2.20% | 2.00%
Europe [Member] |  |
Disclosure of defined benefit plans [Line Items] |  |
Discount rate | 1.50% | 1.40%
Inflation | 1.70% | 1.60%
Rate of increase in pensions | 1.70% | 1.40%
Rate of increase in salaries | 1.90% | 2.40%

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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 2016-01-13 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_144&doctype=Standard -URIDate 2016-03-31 + 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 2016-01-13 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_144&doctype=Standard -URIDate 2016-03-31 + Details
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- Definition The expected rate of increases in pension 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 2016-01-13 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_144&doctype=Standard -URIDate 2016-03-31 + 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 2016-01-13 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_144&doctype=Standard -URIDate 2016-03-31 + Details
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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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