Stock-Based Compensation - Stock options, fair value assumptions (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023
Stock-Based Compensation
Fair value of options granted (in dollars per share)	$ 0.68	$ 2.02
Employee Stock Option
Stock-Based Compensation
Risk-free interest rate, minimum (as a percent)	3.70%	3.60%
Risk-free interest rate, maximum (as a percent)	4.60%	4.40%
Expected dividend yield (as a percent)	0.00%	0.00%
Expected volatility, minimum (as percentage)	87.70%	81.70%
Expected volatility, maximum (as percentage)	91.40%	87.30%
Unrecognized stock-based compensation expense	$ 7.0
Weighted-average period for unrecognized compensation expense to be recognized	2 years 1 month 6 days
Employee Stock Option \| Minimum
Stock-Based Compensation
Expected term (in years)	5 years 6 months	5 years 6 months
Employee Stock Option \| Maximum
Stock-Based Compensation
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days

Weighted-average period over which cost not yet recognized is expected to be recognized for 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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Amount of cost to be recognized for option under share-based payment arrangement.

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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 maximum 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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The estimated measure of the minimum 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 maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

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The minimum 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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- 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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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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