Stock-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value of options granted, per share	$ 4.78	$ 4.75
Grant date fair value of options vested	$ 1,200,000	$ 1,100,000
Aggregate intrinsic value of options exercised	1,900,000	1,600,000
Unrecognized compensation cost	$ 34,100,000
Weighted average period for recognition of compensation costs	3 years 2 months 12 days
RSUs Granted	651,392
RSUs Vested	21,149
Stock-based compensation expense capitalized	$ 0	$ 0
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average period for recognition of compensation costs	2 years 3 months 18 days
Total grant date fair value of RSUs	$ 5,000,000
Total fair value of RSUs vested	100,000
RSUs Granted		0
RSUs Vested		0
Unrecognized stock based compensation cost	$ 16,200,000
Shares expected to vest	2,191,333

Represents the compensation cost capitalized during the period arising from equity-based compensation arrangements (for example, shares of stock, units, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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-Publisher FASB
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-SubTopic 10
-Section 50
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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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- Definition

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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- Definition

Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options expected to vest number.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options grants in period grant date fair value.

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