Employee Benefit Plans - Summary of Estimated Fair Value of ESPP Purchase Rights Using a Black-Scholes Option Pricing Model Assumptions (Details) - $ / shares	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	6 years	6 years
Risk-free interest rate	2.20%	3.00%
Volatility	46.00%	49.00%	46.00%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Fair value of common stock	$ 16.48	$ 13.65	$ 16.48	$ 13.65
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)			5 years 10 months 24 days	5 years 9 months 18 days
Fair value of common stock	12.35	13.20	$ 12.35	$ 13.20
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)			6 years	6 years
Fair value of common stock	$ 16.48	$ 13.65	$ 16.48	$ 13.65
2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%		0.00%
Fair value of common stock	$ 16.98		$ 16.98
2018 Employee Stock Purchase Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	6 months		6 months
Risk-free interest rate	2.10%		2.10%
Volatility	40.00%		40.00%
2018 Employee Stock Purchase Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	2 years		2 years
Risk-free interest rate	2.40%		2.40%
Volatility	45.00%		45.00%

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.

+ References

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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

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the 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=109197908&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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