Stockholders' Equity - Summary of Stock Option Activity under its Stock Plans (Detail)	6 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Available for Grant, Outstanding Beginning Balance	3,170,577
Available for Grant, Shares authorized	2,950,000
Shares Available for Grant, Granted	(1,175,768)
Shares Available for Grant, Exercised	86,343
Shares Available for Grant, Forfeited and expired	377,187
Shares Available for Grant, Outstanding Ending Balance	5,408,339
Shares, Options Outstanding, Beginning Balance	7,114,225
Shares, Options Outstanding, authorized	0
Shares, Options Outstanding, Granted	923,234
Shares, Options Outstanding, Exercised	(272,669)
Shares, Options Outstanding, Forfeited and expired	(377,187)
Shares, Options Outstanding, Ending Balance	7,387,603
Shares, Vested and expected to vest, net of estimated forfeiture at June 30, 2021	7,148,054
Shares, Exercisable at June 30, 2021	4,939,401
Weighted Average Exercise Price, Options Outstanding, Beginning Balance | $ / shares	$ 14.61
Weighted Average Exercise Price, Options Outstanding, Granted | $ / shares	54.57
Weighted Average Exercise Price, Options Outstanding, Exercised | $ / shares	10.55
Weighted Average Exercise Price, Options Outstanding, Forfeited and expired | $ / shares	25.91
Weighted Average Exercise Price, Options Outstanding, Ending Balance | $ / shares	19.17
Weighted Average Exercise Price, Vested and expected to vest, net of estimated forfeiture at June 30, 2021 | $ / shares	18.41
Weighted Average Exercise Price, Exercisable at June 30, 2021 | $ / shares	$ 10.79
Options Outstanding, Weighted Average Remaining Contractual Term	6 years 2 months 26 days
Weighted Average Remaining Contractual Term, Vested and expected to vest, net of estimated forfeiture at June 30, 2021	6 years 1 month 24 days
Weighted Average Remaining Contractual Term, Exercisable at June 30, 2021	5 years 25 days
Aggregate Intrinsic Value, Outstanding, Ending Balance | $	$ 248,284,784
Aggregate Intrinsic Value, Vested and expected to vest, net of estimated forfeiture at June 30, 2021 | $	244,644,226
Aggregate Intrinsic Value, Exercisable at June 30, 2021 | $	$ 200,242,329