Stockholders' Equity - Summary of Stock Option Activity under its Stock Plans (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Available for Grant, Outstanding Beginning Balance	1,708,516
Available for Grant, Shares authorized	2,000,000
Shares Available for Grant, Granted	(2,531,063)
Shares Available for Grant, Exercised	125,526
Shares Available for Grant, Forfeited and expired	889,566
Shares Available for Grant, Outstanding Ending Balance	2,192,545
Shares, Options Outstanding, Beginning Balance	10,720,200
Shares, Options Outstanding, authorized	0
Shares, Options Outstanding, Granted	2,301,242
Shares, Options Outstanding, Exercised	(2,850,642)
Shares, Options Outstanding, Forfeited and expired	(882,899)
Shares, Options Outstanding, Ending Balance	9,287,901
Shares, Vested and expected to vest, net of estimated forfeiture at December 31, 2019	8,966,722
Shares, Exercisable at December 31, 2019	5,750,443
Weighted Average Exercise Price, Options Outstanding, Beginning Balance | $ / shares	$ 8.39
Weighted Average Exercise Price, Options Outstanding, Granted | $ / shares	11.69
Weighted Average Exercise Price, Options Outstanding, Exercised | $ / shares	7.74
Weighted Average Exercise Price, Options Outstanding, Forfeited and expired | $ / shares	7.97
Weighted Average Exercise Price, Options Outstanding, Ending Balance | $ / shares	9.44
Weighted Average Exercise Price, Vested and expected to vest, net of estimated forfeiture at December 31, 2019 | $ / shares	9.38
Weighted Average Exercise Price, Exercisable at December 31, 2019 | $ / shares	$ 8.62
Options Outstanding, Weighted Average Remaining Contractual Term	6 years 6 months 14 days
Weighted Average Remaining Contractual Term, Vested and expected to vest, net of estimated forfeiture at December 31, 2019	6 years 5 months 12 days
Weighted Average Remaining Contractual Term, Exercisable at December 31, 2019	5 years 1 month 20 days
Aggregate Intrinsic Value, Outstanding, Ending Balance | $	$ 279,636,183
Aggregate Intrinsic Value, Vested and expected to vest, net of estimated forfeiture at December 31, 2019 | $	270,570,850
Aggregate Intrinsic Value, Exercisable at December 31, 2019 | $	$ 177,869,577