Stock-Based Compensation - Summary of Weighted-Average Assumptions of Fair Value Awards (Detail)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.89%	1.10%	0.47%
Risk-free interest rate, maximum	2.52%	2.28%	1.10%
Expected term	6 months	6 months	6 months
Expected volatility, minimum	43.00%	49.00%	61.00%
Expected volatility, maximum	67.00%	65.00%	80.00%
Dividend yield	0.00%	0.00%	0.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.39%	2.55%	1.70%
Risk-free interest rate, maximum	2.56%	3.03%	2.27%
Expected volatility, minimum	59.00%	59.00%	60.00%
Expected volatility, maximum	61.00%	62.00%	65.00%
Dividend yield	0.00%	0.00%	0.00%
Employee Stock Option \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	5 years	5 years	5 years
Employee Stock Option \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days
Performance Stock Options (PSOs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.43%
Expected term	6 years
Expected volatility	61.00%
Dividend yield	0.00%	0.00%	0.00%

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 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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- Definition

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

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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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- Definition

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

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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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)
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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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