Deferred income tax - Consolidated statement of financial position (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax
Deferred income tax asset	$ 73,850	$ 74,556
Deferred income tax liability	38,319	28,959
Deferred tax liability (asset)	$ 35,531	$ 45,597	$ 6,883

The amounts of income taxes recoverable in future periods in respect of: (a) deductible temporary differences; (b) the carryforward of unused tax losses; and (c) the carryforward of unused tax credits. [Refer: Temporary differences [member]; Unused tax credits [member]; Unused tax losses [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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