Stockholders' Equity and Stock-Based Compensation - Summary of Fair Value of Employee and Non-employee Stock Options Granted (Details) - $ / shares	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term in years	6 years 21 days	6 years 25 days	6 years 21 days	6 years 25 days
Expected volatility	72.48%	72.27%	72.29%	72.31%
Risk-free interest rate	0.45%	2.07%	0.57%	2.10%
Weighted average fair value of share-based awards granted	$ 29.03	$ 18.62	$ 29.65	$ 18.22
Non Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term in years	6 years 21 days		6 years 21 days	6 years 29 days
Expected volatility	72.48%		72.45%	73.54%
Risk-free interest rate	0.41%		0.44%	2.74%

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.

+ References

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.

+ 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
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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