Stock Plans and Stock-Based Compensation - Additional Information (Details) - USD ($)			1 Months Ended	12 Months Ended
	Jan. 01, 2022	Jan. 01, 2019	Mar. 31, 2018	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of shares exercised				$ 17,400,000	$ 6,800,000	$ 200,000
Fair value of shares vested				$ 52,400,000	$ 16,800,000	$ 7,800,000
Weighted-average grant date fair value of stock options granted				$ 22.05	$ 11.57	$ 6.33
Options granted				3,758,769
Common stock, shares outstanding				70,781,736	65,114,685
Share-based compensation, vested stock options				37,250	31,986	372,774
Description of expected term simplified method				The Company has opted to use the “simplified method” for estimating the expected term of options, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option (generally 10 years).
Expected term				10 years
Expected dividend yield				0.00%
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of RSUs granted				$ 34.05	$ 27.77
Total grant date fair value of shares granted						$ 0
Total grant date fair value of shares vested				$ 12,100,000	$ 100,000	$ 0
Non-Employee Stock-Based Compensation
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares not vested and subject to repurchase				1,291	21,165	308,596
Stock based compensation expense				$ 200,000	$ 700,000	$ 900,000
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized employee compensation costs				$ 102,900,000
Non-vested stock option recognized weighted average period				2 years 6 months
Expected term				6 years 7 days	6 years 7 days	6 years 7 days
Expected dividend yield				0.00%	0.00%	0.00%
2015 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares not vested and subject to repurchase				9,946	165,133
Cash received from early exercise of unvested options				$ 100,000	$ 700,000
Award vesting period				48 months
Total shares of authorized common stock reserved for future issuance			709,558
2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares issued or transferred			3,570,000
Total shares of authorized common stock reserved for future issuance				2,226,271
2018 Equity Incentive Plan | Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares not vested and subject to repurchase				1,076,088	738,650
Weighted-average grant date fair value of RSUs granted				$ 34.05
2018 Equity Incentive Plan | Restricted Stock Units | Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period				4 years
Vesting interval period				annually or quarterly
2018 Equity Incentive Plan | Restricted Stock Units | Directors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting interval period				annually
2018 Equity Incentive Plan | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for issuance under evergreen provision	2,831,269
2018 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for issuance under evergreen provision		3,570,000
Percentage of common stock outstanding		4.00%
2020 Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares issued or transferred				5,000,000	1,000,000		3,000,000
Total shares of authorized common stock reserved for future issuance				3,743,219
Shares issued				2,288,000
2018 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase date of fair market value trading days			24 months
Total shares of authorized common stock reserved for future issuance			714,000	1,610,979
2018 Employee Stock Purchase Plan | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for issuance under evergreen provision	707,817
2018 Employee Stock Purchase Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase price of common stock as percentage of market value			85.00%
Number of shares of common stock that may be purchased by an employee on any purchase date			3,000
Number of shares that may be purchased in any calendar year			$ 25,000
Percentage of common stock shares outstanding		1.00%
Common stock, shares outstanding		1,071,000