Share-based compensation - Fair Value Assumptions (Details) |
12 Months Ended | ||
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Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
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| Assumptions used to estimate the fair values of the share options granted using the Black-Scholes option-pricing model | |||
| Expected term (in years) | 5 years | 5 years | 5 years |
| Expected dividend yield (as a percent) | 0.00% | 0.00% | 0.00% |
| Minimum | |||
| Assumptions used to estimate the fair values of the share options granted using the Black-Scholes option-pricing model | |||
| Expected volatility (as a percent) | 90.00% | 69.00% | 66.00% |
| Risk free rate (as a percent) | 0.00% | 0.22% | 0.90% |
| Maximum | |||
| Assumptions used to estimate the fair values of the share options granted using the Black-Scholes option-pricing model | |||
| Expected volatility (as a percent) | 99.00% | 73.00% | 69.00% |
| Risk free rate (as a percent) | 0.42% | 0.90% | 1.15% |
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- References No definition available.
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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