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Share-Based Compensation - Schedule of Fair Value of Stock Option Award Granted Estimated on Date of Grant Using the Black-Scholes-Merton Option Pricing Model (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	1.60%	2.60%	1.90%
Weighted average volatility	62.60%	56.10%	64.20%
Expected life (in years)	8 years	5 years	5 years 2 months 12 days
Weighted average grant date fair value per share of options granted	$ 13.78	$ 7.09	$ 4.81

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

+ 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)(iv)
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Rate of weighted-average expected volatility for award under share-based payment arrangement.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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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.

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-SubTopic 10
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