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Pensions and Other Post-employment Benefit Obligations - Summary of Actuarial Assumptions (Detail) | Dec. 31, 2018 | Dec. 31, 2017
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Switzerland [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Rate of increase in salaries | 1.50% | 1.50%
Discount rate | 0.80% | 0.65%
United States [member] | Hourly pension [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Rate of increase in salaries | 2.20% | 2.20%
United States [member] | Salaried pension [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Rate of increase in salaries | 3.80% | 3.80%
Discount rate | 4.45% | 3.80%
United States [member] | Other post employment benefit [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Rate of increase in salaries | 3.80% | 3.80%
United States [member] | Other benefits [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Rate of increase in salaries | 3.80% | 3.80%
France [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Rate of increase in pension | 2.00% | 2.00%
France [member] | Retirements [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Discount rate | 1.65% | 1.50%
France [member] | Other benefits [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Discount rate | 1.35% | 1.20%
Germany [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Rate of increase in salaries | 2.75% | 2.75%
Rate of increase in pension | 1.70% | 1.70%
Discount rate | 1.70% | 1.60%
Bottom of range [member] | United States [member] | Hourly pension [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Discount rate | 4.40% | 3.70%
Bottom of range [member] | United States [member] | Other post employment benefit [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Discount rate | 4.40% | 3.70%
Bottom of range [member] | United States [member] | Other benefits [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Discount rate | 4.25% | 3.60%
Bottom of range [member] | France [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Rate of increase in salaries | 1.50% | 1.50%
Top of range [member] | United States [member] | Hourly pension [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Discount rate | 4.45% | 3.75%
Top of range [member] | United States [member] | Other post employment benefit [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Discount rate | 4.55% | 3.85%
Top of range [member] | United States [member] | Other benefits [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Discount rate | 4.40% | 3.70%
Top of range [member] | France [member] |  |
Disclosure of sensitivity analysis for actuarial assumptions [line items] |  |
Rate of increase in salaries | 2.50% | 1.75%

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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 2018-01-01 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_144&doctype=Standard -URIDate 2018-03-16 + 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 2018-01-01 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_144&doctype=Standard -URIDate 2018-03-16 + 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 2018-01-01 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_144&doctype=Standard -URIDate 2018-03-16 + Details
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