Stock-Based Compensation - Black-Scholes-Merton Option Pricing Model for Stock Options Granted (Detail)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected dividend yield	0.00%	0.00%	0.00%
Weighted average expected volatility	58.00%	58.00%	57.00%
Weighted average expected term (years)	5 years 11 months 12 days	5 years 10 months 24 days	5 years 10 months 20 days
Weighted average risk-free rate	2.26%	2.68%	1.97%

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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.

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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

Weighted average expected volatility rate of share-based compensation awards.

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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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