Common stock exchange ratio.

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Net proceeds from issuance public offering.

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Purchase plan offering period.

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Purchase plan purchase period.

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Share based compensation arrangement by share based payment award number of vesting installment.

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Share based compensation arrangement by share based payment award options expiration term.

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Share based compensation arrangement by share based payment award options maximum term for specified stock holder.

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Share based compensation arrangement by share based payment award purchase price of common stock percent for specified stockholder.

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Specified stockholder ownership percentage.

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Aggregate number of common shares reserved for future issuance.

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Amount of cash outflow to satisfy an employee's income tax withholding obligation as part of a net-share settlement of a share-based award.

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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The weighted average fair value at grant date for nonvested equity-based awards issued 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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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 maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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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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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Percentage of vesting of share-based compensation awards.

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Intrinsic value of equity-based compensation awards vested. Excludes stock and unit options.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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Per share or per unit amount of equity securities issued.

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For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

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Number of new stock issued during the period.

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Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

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Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Apr. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2018 shares	Apr. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) installment $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred shares authorized (in shares)					5,000,000	5,000,000
Net proceeds from issuance of common stock, after deducting offering expenses \| $					$ 136,308	$ 215,758	$ 81,573
Stock option maximum term					6 years 6 months 14 days
Specified stockholder ownership percentage					10.00%
Purchase price of common stock percent under stock incentive plans for specified stockholder					110.00%
Stock option maximum term for specified stockholder					5 years
Share of common stock subject to a stock option or stock appreciation right (in shares)					100.00%
Additional equity award (in shares)					4,530,288
Intrinsic value of options exercised \| $					$ 4,700	27,000	12,300
Options vested and expected to vest, aggregate intrinsic value \| $					7,500	24,500	71,700
Options exercisable, aggregate intrinsic value \| $					$ 5,442
Restricted stock units awarded (in shares)					834,745
Total payments for the employees' tax obligations to taxing authorities \| $					$ 422	$ 254	$ 654
Shares reserved for issuance of future awards (in shares)					2,757,600
Share-Based Compensation Awards, Tranche 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage					33.33%
Share-Based Compensation Awards, Tranche 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage					33.33%
2013 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance of future awards (in shares)					6,691,209
Amended and Restated 2013 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional equity award (in shares)			0
2018 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of fair value per share of common stock on option grant date					100.00%
Stock options vesting period					4 years
Stock options expiration term					10 years
Fixed ratio shares of common stock					1.33
2010 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of fair value per share of common stock on option grant date		85.00%
Stock reserved for issuance under plan (in shares)		4,600,000
Purchase plan offering period		2 years
Purchase plan purchase period		6 months
Maximum \| 2018 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option maximum term					10 years
Employee Stock Options \| 2018 Stock Incentive Plan \| Share-Based Compensation Awards, Tranche 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage					25.00%
Employee Stock Options \| 2018 Stock Incentive Plan \| Share-Based Compensation Awards, Tranche 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage					2.08%
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units awarded (in shares)					834,745	346,055	12,600
Grant date fair value per award of restricted stock units (in dollars per share) \| $ / shares					$ 9.49	$ 17.87	$ 15.85
Share-based compensation arrangement by share-based payment award, number of vesting installment \| installment					3
Aggregate fair value of RSUs vested in period \| $					$ 2,000	$ 600	$ 1,200
Shares withheld from issuance in order to pay employee taxes (in shares)					39,160	20,193	42,243
Restricted Stock Units (RSUs) \| Share-Based Compensation Awards, Tranche 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage					33.33%
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock under public offering, net of issuance costs (in shares)	12,700,000		14,200,000	11,500,000	12,650,000	14,156,500	12,371,149
Public offering price of common stock issued (in dollars per share) \| $ / shares	$ 11.50		$ 16.25	$ 7.25
Net proceeds from issuance of common stock, after deducting offering expenses \| $	$ 136,300		$ 215,800	$ 78,100