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.

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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.

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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.

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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.

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No definition available.

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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

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

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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.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-Name Accounting Standards Codification
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-Section S99
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-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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Stockholders' Equity and Employee Benefit Plans - Summary of Estimated Fair Value of Stock Options and ESPP (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	2.40%
Risk-free interest rate, maximum	2.90%
Volatility, minimum	38.00%
Volatility, maximum	40.00%
Fair value of common stock	$ 12.89
Minimum \| 2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	7 months 6 days
Maximum \| 2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	2 years 1 month 6 days
Out-of-the-Money Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum		2.30%	1.70%
Risk-free interest rate, maximum		2.40%	2.00%
Volatility		50.00%
Volatility, minimum			51.00%
Volatility, maximum			54.00%
Dividend yield		0.00%	0.00%
Out-of-the-Money Stock Option \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)		5 years 8 months 12 days	7 years
Fair value of common stock		$ 11.84	$ 12.21
Out-of-the-Money Stock Option \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)		6 years 1 month 6 days	9 years 2 months 12 days
Fair value of common stock		$ 12.33	$ 12.28
At-the-Money Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	2.70%
Risk-free interest rate, maximum	3.00%
Volatility, minimum	43.00%
Volatility, maximum	60.00%
Dividend yield	0.00%
At-the-Money Stock Option \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	5 years 9 months 18 days
Fair value of common stock	$ 12.00
At-the-Money Stock Option \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	6 years 1 month 6 days
Fair value of common stock	$ 13.65