Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost related to unvested stock options and RSU	$ 35,500,000
Weighted-average period of unvested stock options and RSU	2 years 8 months 19 days
Capitalized stock-based employee compensation expense	$ 0	$ 0	$ 0
Weighted-average estimated fair value per share of options granted (in dollars per share)	$ 5.25	$ 6.37	$ 11.39
Issuance of common stock under employee stock purchase plan (in shares)	274,382	249,364	328,710
Stock issued under employee stock purchase plans, average exercise price (in dollars per share)	$ 7.34	$ 8.53	$ 4.51
Weighted-average estimated fair value of shares purchased under ESPP plan (in dollars per share)	$ 8.02	$ 4.70	$ 7.07
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost related to unvested stock options and RSU	$ 17,100,000
Weighted-average period of unvested stock options and RSU	2 years 25 days

Employee stock purchase plan rights weighted average estimated fair value.

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Stock issued under employee stock purchase plans average exercise price.

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- Definition

Amount of cost capitalized for award under share-based payment arrangement.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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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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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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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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Number of shares issued during the period as a result of an employee stock purchase plan.

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