Equity Incentive Plans - Summary of Stock Option Activity Under 2009 Plan and 2019 Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Subject to Outstanding Options, Options outstanding, Beginning Balance	14,433,560
Shares Subject to Outstanding Options, Options granted	1,635,608
Shares Subject to Outstanding Options, Options forfeited or cancelled	(328,594)
Shares Subject to Outstanding Options, Options expired	(10,050)
Shares Subject to Outstanding Options, Options exercised	(2,183,640)
Shares Subject to Outstanding Options, Options outstanding, Ending Balance	13,546,884
Shares Subject to Outstanding Options, Options vested and exercisable	6,853,224
Weighted Average Exercise Price per Share, Options outstanding, Beginning Balance	$ 12.82
Weighted Average Exercise Price per Share, Options granted	45.33
Weighted Average Exercise Price per Share, Options forfeited or cancelled	15.47
Weighted Average Exercise Price per Share, Options expired	0.19
Weighted Average Exercise Price per Share, Options exercised	6.61
Weighted Average Exercise Price per Share, Options outstanding, Ending Balance	17.69
Weighted Average Exercise Price per Share, Options vested and exercisable	$ 8.56
Aggregate Intrinsic Value, Option outstanding	$ 319,063	$ 668,458
Aggregate Intrinsic Value, Options vested and exercisable	$ 217,592