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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate number of common shares reserved for future issuance.

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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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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Description of terms of share-based payment arrangement. Includes, but is not limited to, type of award or grantee and reason for issuance.

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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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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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Number of additional shares authorized for issuance under share-based payment arrangement.

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Number of shares authorized for issuance under share-based payment arrangement.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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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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Gross number of share options (or share units) granted during the period.

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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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Maximum number of shares that may be issued in accordance with the plan as a proportion of outstanding capital stock.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of options vested.

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Purchase price of common stock expressed as a percentage of its fair value.

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

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Equity Incentive Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Closing price of common stock	$ 5.19
Aggregate intrinsic value of options exercised	$ 100	$ 300	$ 600
Expected dividend yield	0.00%
Common Stock Reserved for Issuance	7,884,002	5,299,475
Number of additional shares authorized	2,543,924
Options available for future grants	1,327,645	1,021,109
Issuance of common stock upon ESPP purchase	$ 257	$ 186	130
Stock options granted	1,866,785
Stock-based compensation expense	$ 7,901	$ 5,973	$ 5,679
Total unrecognized compensation expense	$ 12,600
Weighted-average period for recognition (in years)	2 years 8 months 12 days
Weighted average period expected to recognized compensation expense (in years)	2 years 8 months 12 days
Employees Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of employee option grants	$ 5.58	$ 4.78	$ 8.98
Grant date fair value of employee options vested	6,900,000	5,600,000	5,700,000
Performance Stock Units (PSU) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of employee option grants	$ 7.92
Options available for future grants	270,000
Stock-based compensation expense	$ 200	$ 0
Restricted Stock Units, Unvested [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of employee option grants	$ 9.16
Stock options granted	371,500
Stock-based compensation expense	$ 900	$ 200
Total unrecognized compensation expense	$ 4,300
Weighted-average period for recognition (in years)	2 years 9 months 18 days
Weighted average period expected to recognized compensation expense (in years)	2 years 9 months 18 days
Restated 2013 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Issuance of common stock authorized	6,399,366
2013 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common Stock Reserved for Issuance	783,831			100,000
Percentage increase in number of shares of common stock reserved for issuance	1.00%
Number of additional shares authorized	165,000
Options available for future grants	671,172
Issuance of common stock upon ESPP purchase, Shares	37,619	25,645	15,701
Issuance of common stock upon ESPP purchase	$ 300	$ 200	$ 100
Share-based compensation arrangement by share-based payment award, description	The number of shares of common stock initially reserved for issuance under the 2013 ESPP was 100,000 shares with an automatic annual increase to the shares issuable under the 2013 ESPP to the lower of (i) 1% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, and (ii) 165,000 shares of common stock, unless a lower number determined by the board of directors. As of December 31, 2021, a total of 783,831 shares are reserved for issuance and 671,172 shares available for future issuance under the 2013 ESPP. During the years ended December 31, 2021, 2020 and 2019, employees purchased 37,619 shares for $0.3 million, 25,645 shares for $0.2 million and 15,701 shares for $0.1 million, respectively, under the 2013 ESPP.
Minimum [Member] \| Restated 2013 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Threshold ownership percentage of shareholder for grant of options at pre determined exercise price	10.00%
Minimum [Member] \| Holders Of Ten Percent Or More Of Voting Power \| Restated 2013 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	110.00%
Maximum [Member] \| Restated 2013 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual terms of options granted under the Plan	10 years