Stock-Based Compensation - Employee Stock Purchase Plan (Details) - $ / shares	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value
Risk-free interest rate, maximum				2.60%
ESPP
Fair Value
Risk-free interest rate, minimum	0.20%	1.30%	0.20%	1.20%
Risk-free interest rate, maximum	2.50%	2.60%	2.60%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Volatility, minimum	77.50%	59.70%	66.60%	52.20%
Volatility, maximum	189.70%	171.60%	189.70%	171.60%
Expected forfeiture rate	0.00%	0.00%	0.00%	0.00%
Additional disclosures:
Authorized (in shares)	600,000		600,000
Subscription rate cap	15.00%		15.00%
Maximum discount rate			85.00%
Shares available for grant	255,596		255,596
ESPP \| Minimum
Fair Value
Weighted average (per share)	$ 3.08	$ 2.57	$ 2.57	$ 2.57
Expected term (in years)	6 months	6 months	6 months	6 months
ESPP \| Maximum
Fair Value
Weighted average (per share)	$ 92.67	$ 35.00	$ 92.67	$ 35.00
Expected term (in years)	2 years	2 years	2 years	2 years

Estimated rate of forfeitures.

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- Definition

Discount rate from fair value on purchase date that participants pay for shares.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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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.

+ References

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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.

+ References

No definition available.

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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.

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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

+ References

No definition available.

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- Definition

The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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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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