Earnings per share - Earnings per share, basic and diluted (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Ordinary Shares
Earnings per share [line items]
Basic earnings (loss) per share (USD per share)	$ 0.1984	$ 0.4698	$ 0.1720
Diluted earnings (loss) per share (USD per share)	0.1973	0.4667	0.1710
American Depositary Share
Earnings per share [line items]
Basic earnings (loss) per share (USD per share)	1.19	2.82	1.03
Diluted earnings (loss) per share (USD per share)	$ 1.18	$ 2.80	$ 1.03

The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator) divided by the weighted average number of ordinary shares outstanding during the period (the denominator).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 33
-IssueDate 2018-01-01
-Paragraph 66
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-URIDate 2018-03-16

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- Definition

The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator), divided by the weighted average number of ordinary shares outstanding during the period (the denominator), both adjusted for the effects of all dilutive potential ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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