Common stock capital shares value reserved for future issuance.

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Common stock exchange ratio.

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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 additional shares reserved for issuance.

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Share based compensation arrangement by share based payment award number of shares initially reserved for issuance.

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

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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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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Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands		1 Months Ended		12 Months Ended
	Jun. 22, 2015 shares	Apr. 30, 2018 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) Installment $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Nov. 10, 2017 shares	May 31, 2017 USD ($)	Dec. 07, 2016 USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred shares authorized				5,000,000
Net proceeds from issuance of common stock, after deducting offering expenses \| $				$ 215,758	$ 81,573
Stock option maximum term				5 years 4 months 20 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				100.00%
Fixed ratio shares of common stock				1.33
Additional equity award				3,115,078
Intrinsic value of options exercised \| $				$ 27,000	12,300	$ 100
Options outstanding, Aggregate Intrinsic Value \| $				24,468
Options exercisable, Aggregate Intrinsic Value \| $				12,702
Options vested and expected to vest, aggregate intrinsic value \| $				$ 24,500	71,700	0
Restricted stock units awarded				346,055
Total payments for the employees' tax obligations to taxing authorities \| $				$ 254	$ 654	$ 776
Share-Based Compensation Awards, Tranche 2 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted vesting percentage				0.33%
Share-Based Compensation Awards, Tranche 3 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted vesting percentage				0.33%
2013 Stock Incentive Plan [Member]
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
Stock reserved for issuance under plan				14,100,000
Additional shares authorized under 2013 stock incentive plan	5,300,000			4,400,000
Shares reserved for issuance of future awards				9,491,418
2004 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock reserved for issuance under plan				9,700,000
Amended and Restated 2013 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock reserved for issuance under plan							1,000,000
Additional equity award		0
2018 Stock Incentive Plan [Member]
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
Share of common stock subject to a stock option or stock appreciation right				100.00%
Fixed ratio shares of common stock				1.33
2010 Employee Stock Purchase Plan [Member]
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				4,600,000
Purchase plan offering period				2 years
Purchase plan purchase period				6 months
Shares reserved for issuance of future awards				3,006,964
Maximum [Member] \| 2013 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option maximum term				10 years
Maximum [Member] \| 2018 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option maximum term				10 years
Employee Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares subject to repurchase rights				0
Employee Stock Options [Member] \| 2013 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based vesting rights				Options granted under the 2013 Plan generally vest over four years at a rate of 25% one year from the grant date and one thirty-sixth per month thereafter and expire ten years after the grant, or earlier upon employment termination.
Stock options granted vesting percentage				25.00%
Employee Stock Options [Member] \| 2018 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based vesting rights				Generally, stock options granted under the 2018 Plan vest over four years at a rate of twenty-five percent (25%) on the one-year anniversary of the date of grant and one forty-eighth (1/48) per month thereafter and expire ten years after the date of grant, or earlier upon termination of employment or services to the Company
Stock options granted vesting percentage				25.00%
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based vesting rights				These awards generally vest as follows: one-third of the award will vest in a series of three successive equal annual installments.
Restricted stock units awarded				346,055	12,600	60,000
Grant date fair value per award of restricted stock units \| $ / shares				$ 17.87	$ 15.85	$ 5.16
Share-based compensation arrangement by share-based payment award, number of vesting installment \| Installment				3
Aggregate fair value of RSUs vested in period \| $				$ 600	$ 1,200	$ 4,800
Shares withheld from issuance in order to pay employee taxes				20,193	42,243	165,181
Restricted Stock Units (RSUs) [Member] \| Share-Based Compensation Awards, Tranche 1 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted vesting percentage				0.33%
ATM Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock issuable and sellable under offering agreement \| $				$ 75,000				$ 75,000	$ 75,000
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total shares issued		14,200,000	11,500,000	14,156,500	12,371,149
Public offering price of common stock issued \| $ / shares		$ 16.25	$ 7.25
Net proceeds from issuance of common stock, after deducting offering expenses \| $		$ 215,800	$ 78,100