Restructuring Costs - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Analysis of income and expense [abstract]
Restructuring costs	$ 4,000,000	$ 50,000,000
Restructuring costs related to accelerated vesting of share based compensation	0	4,000,000
Amount of restructuring settled within the year	2,000,000	16,000,000
Amount of restructuring costs remaining to be paid as at balance sheet date	$ 18,000,000	$ 34,000,000

The amount of expense relating to restructuring. Restructuring is a programme that is planned and controlled by management and materially changes either the scope of a business undertaken by an entity or the manner in which that business is conducted. Such programmes include: (a) the sale or termination of a line of business; (b) closure of business locations in a country or region or the relocation of activities from one country or region to another; (c) changes in management structure; and (d) fundamental reorganisations that have a material effect on the nature and focus of the entity's operations.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 98
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_98_b&doctype=Standard
-URIDate 2017-03-09

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration