Stock-Based Compensation - (Stock Option) - Additional Information (Detail) $ / shares in Units, $ in Thousands	6 Months Ended
Jun. 30, 2020 USD ($) installment $ / shares	Jun. 30, 2019 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation option awards contractual term	10 years
Portion of initial stock options granted to employees that vests on employee's first anniversary	25.00%
Portion of initial stock options granted to employees that vests ratably over three years after completion of first year of service	75.00%
Number of vesting equal installments \| installment	36
Vesting period for subsequent stock options granted to directors	4 years
Options granted, weighted average fair value per share (in dollars per share) \| $ / shares	$ 5.65	$ 11.16
Proceeds from exercise of employee stock options	$ 4,079	$ 3,590
Service option awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses	$ 8,400
Unrecognized compensation expenses, weighted average period	1 year 4 months 24 days

Weighted-average period over which cost not yet recognized is expected to be recognized for 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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Amount of cost to be recognized for option under share-based payment arrangement.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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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- Definition

Percentage of new hire stock option award that vests after one year of service.

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Period which an employee and new director's right to exercise an annual option award is no longer contingent on satisfaction of either a service, market or a performance condition.

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Contractual term of stock option awards.

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Share-based Compensation Arrangement by Share-Based Payment Award, Options, Vesting Period, Number Of Equal Monthly Installments

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