Earnings per share - Earnings per share, basic and diluted (Details) - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Ordinary Shares
Earnings per share [line items]
Basic earnings (loss) per share (USD per share)	$ (1.0042)	$ 0.1984	$ 0.4698
Diluted earnings (loss) per share (USD per share)	(1.0042)	0.1973	0.4667
American Depositary Share
Earnings per share [line items]
Basic earnings (loss) per share (USD per share)	(6.03)	1.19	2.82
Diluted earnings (loss) per share (USD per share)	$ (6.03)	$ 1.18	$ 2.80

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
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-IssueDate 2020-01-01
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-URIDate 2020-01-01

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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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