| Share-based compensation - Options (Details) - $ / shares | 12 Months Ended | ||
|---|---|---|---|
| Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | |
| Options granted on market value at grant date | |||
| Number of options over ordinary shares granted (in shares) | 31,826,293 | 21,300,998 | 15,595,374 | 
| Weighted average fair value of ordinary shares options (in dollars per share) | $ 0.37 | $ 0.70 | $ 0.59 | 
| Options with nominal exercise price | |||
| Number of additional options with a nominal exercise price granted | 24,248,424 | 17,765,778 | 8,282,152 | 
| Weighted average fair value of options with a nominal exercise price | $ 0.51 | $ 0.97 | $ 0.85 | 
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. No definition available. 
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- Definition Gross number of share options (or share units) granted with nominal exercise price during the period. No definition available. 
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- Definition Gross number of share options (or share units) granted during the period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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