Incentive Stock Options and Employee Stock Purchase Plan - Summary of Stock Option Activity (Detail) - Stock Options [Member] $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Number of shares
Number of shares, beginning balance | shares	9,557,391
Number of shares, granted | shares	3,126,560
Number of shares, exercised | shares	(286,899)
Number of shares, forfeited | shares	(154,303)
Number of shares, ending balance | shares	12,242,749	9,557,391
Number of shares, exercisable | shares	5,953,908
Number of shares, vested and expected to vest, ending balance | shares	12,242,749
Weighted average exercise price
Weighted average exercise price, beginning balance | $ / shares	$ 8.79
Weighted average exercise price, granted | $ / shares	21.81
Weighted average exercise price, exercised | $ / shares	8.25
Weighted average exercise price, forfeited | $ / shares	14.68
Weighted average exercise price, ending balance | $ / shares	12.06	$ 8.79
Weighted average exercise price, exercisable | $ / shares	8.14
Weighted average exercise price, vested and expected to vest, ending balance | $ / shares	$ 12.06
Weighted average remaining contractual term
Weighted average remaining contractual term, ending balance	8 years 25 days	7 years 11 months 1 day
Weighted average remaining contractual term, exercisable	7 years 25 days
Weighted average remaining contractual term, vested and expected to vest, ending balance	8 years 25 days
Intrinsic value
Intrinsic value, ending balance | $	$ 189,483	$ 93,256
Intrinsic value, exercisable | $	115,421
Intrinsic value, vested and expected to vest, ending balance | $	$ 189,483