Stock-Based Compensation - Narrative (Detail)	1 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) shares	Dec. 31, 2020 USD ($) purchasePeriod offeringPeriod shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	May 29, 2020 shares	May 28, 2020 shares	May 21, 2019 shares	May 20, 2019 shares	May 31, 2018 shares	Dec. 31, 2013 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance (shares)		21,943,000	9,646,000
Intrinsic value of options exercised | $		$ 5,100,000	$ 22,400,000	$ 11,800,000
Stock-based compensation | $		29,176,000	$ 21,247,000	15,492,000
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation costs | $		$ 60,600,000
Recognition over weighted average periods		2 years 8 months 12 days
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved (shares)					875,000	375,000
Number of additional shares authorized for issuance (shares)					31,250
Common stock reserved for future issuance (shares)		3,899,000	4,926,000
RSU's
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of RSUs that vested | $		$ 5,700,000	$ 1,900,000	$ 4,200,000
Restricted stock units vested (in shares)		220,000
Performance-based stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units vested (in shares)	128,000
Stock-based compensation | $	$ 1,400,000
2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term		10 years
Vesting term		4 years
Shares of common stock reserved (shares)								7,500,000
Restated 2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved (shares)		3,400,000					11,500,000
Percent of additional shares authorized provision		4.00%
Inducement Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved (shares)									637,500	337,500
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Limit on purchases under the ESPP per calendar year | $		$ 25,000
Employee Stock Purchase Plan | Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of each offering period under the ESPP		12 months
Number of purchase periods permitted under the ESPP | purchasePeriod		2
Duration of each purchase period under the ESPP		6 months
Number of offering periods permitted under the ESPP | offeringPeriod		2
Percentage of purchase price (percent)		85.00%
Maximum percentage of employee withholding (percent)		20.00%
Maximum number of shares per employee (shares)		5,000
Common stock reserved for future issuance (shares)		500,000
Number of shares purchased during period (shares)		51,745	28,146	32,679