Equity Incentive Plans - Summary of Stock Option Activity Under 2009 Plan and 2019 Plan (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($)
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Subject to Outstanding Options, Options outstanding, Beginning Balance | shares	14,433,560
Shares Subject to Outstanding Options, Options granted | shares	2,407,629
Shares Subject to Outstanding Options, Options forfeited or cancelled | shares	(744,501)
Shares Subject to Outstanding Options, Options expired | shares	(21,452)
Shares Subject to Outstanding Options, Options exercised | shares	(3,310,804)
Shares Subject to Outstanding Options, Options outstanding, Ending Balance | shares	12,764,432
Shares Subject to Outstanding Options, Options vested and exercisable | shares	7,080,906
Weighted Average Exercise Price per Share, Options outstanding, Beginning Balance | $ / shares	$ 12.82
Weighted Average Exercise Price per Share, Options granted | $ / shares	41.21
Weighted Average Exercise Price per Share, Options forfeited or cancelled | $ / shares	24.48
Weighted Average Exercise Price per Share, Options expired | $ / shares	18.98
Weighted Average Exercise Price per Share, Options exercised | $ / shares	7.04
Weighted Average Exercise Price per Share, Options outstanding, Ending Balance | $ / shares	18.98
Weighted Average Exercise Price per Share, Options vested and exercisable | $ / shares	$ 10.29
Aggregate Intrinsic Value, Option outstanding | $	$ 218,168	$ 668,458
Aggregate Intrinsic Value, Options vested and exercisable | $	$ 170,535