Share-Based Compensation - Stock option valuation assumptions (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-Based Compensation
Weighted average fair value of options granted (in dollars per share)	$ 111.23	$ 72.69
Options exercised	0	0	0
Total fair value of option vested during the period	$ 0.2	$ 0.1
Options
Share-Based Compensation
Dividend yield (as a percent)	0.00%	0.00%
Expected volatility (as a percent)	111.50%	102.50%
Expected term (in years)	4 years	4 years
Options \| Weighted Average
Share-Based Compensation
Risk free interest rate (as a percent)	3.69%	0.72%

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.

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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.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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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.

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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.

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- Definition

Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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- Definition

Number of share options (or share units) exercised during the current period.

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