Income taxes - Summary of Unrecognized Deferred Tax Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Unrecognized deferred tax assets
Tax losses	$ 160,052	$ 167,030
Other deductible temporary differences	11,967	11,253
Total unrecognized deferred tax assets	$ 172,019	$ 178,283

The amount of deferred tax expense or income relating to the creation or reversal of temporary differences. [Refer: Temporary differences [member]; Deferred tax expense (income)]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 12
-IssueDate 2018-01-01
-Paragraph 80
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2018-03-01&anchor=para_80_c&doctype=Standard
-URIDate 2018-03-16

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Period Type:	duration