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Stock Option Plan - Fair Value Assumptions (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield			0.00%
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	83.00%	51.00%
Expected volatility rate, minimum			83.00%	47.00%
Expected volatility rate, maximum			84.00%	51.00%
Risk-free interest rate	1.10%	0.40%
Risk-free interest rate, minimum			0.80%	0.40%
Risk-free interest rate, maximum			1.10%	1.70%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Stock options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 6 months	5 years 6 months	5 years 6 months	5 years 6 months
Stock options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 29 days	6 years 29 days	6 years 29 days	6 years 29 days
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	60.00%	58.00%	60.00%	58.00%
Risk-free interest rate	0.10%	1.10%	0.10%	1.10%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Expected term (in years)	6 months	6 months	6 months	6 months

X

- 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.

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-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
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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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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 risk-free interest rate assumption that is used in valuing an option on its own shares.

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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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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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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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