Retirement Benefit Obligations - Summary of Average Duration and Scheme Composition (Detail) - yr	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Eurozone [member]
Disclosure of defined benefit plans [Line Items]
Average duration of defined benefit obligation (years)	17.8	17.1	14.7
Active plan participants	72.00%	63.00%	64.00%
Deferred plan participants	9.00%	12.00%	12.00%
Retirees	19.00%	25.00%	24.00%
Switzerland [member]
Disclosure of defined benefit plans [Line Items]
Average duration of defined benefit obligation (years)	17.2	18.6	18.0
Active plan participants	84.00%	84.00%	85.00%
Retirees	16.00%	16.00%	15.00%
United States and Canada [member]
Disclosure of defined benefit plans [Line Items]
Average duration of defined benefit obligation (years)	12.2	13.1	14.0
Active plan participants	40.00%	41.00%	45.00%
Deferred plan participants	16.00%	17.00%	17.00%
Retirees	44.00%	42.00%	38.00%

Allocation Of Defined Benefit Obligation By Participant Active Plan Participant

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- Definition

Allocation Of Defined Benefit Obligation By Participant Deferred Plan Participant

+ References

No definition available.

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- Definition

Allocation Of Defined Benefit Obligation By Participant Retirees

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No definition available.

+ 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.

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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 2016-01-13
-Paragraph 147
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_147_c&doctype=Standard
-URIDate 2016-03-31

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