Stock Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended			9 Months Ended
	Jan. 01, 2019	Mar. 31, 2018	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares issued to the plan						55,234
Aggregate proceeds from shares issued under the plan						$ 938	$ 829
Stock-based compensation			$ 3,346		$ 1,987	9,682	5,199
Total intrinsic value of options exercised						$ 500	$ 1,400
Weighted-average grant date fair value per share for options granted						$ 10.73	$ 14.70
Remaining shares subject to repurchase			4,102			4,102		21,666
Liability for unvested common shares subject to repurchase included in accrued expenses and other liabilities			$ 16			$ 16		$ 37
Accrued Expenses and Other Liabilities
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Liability for unvested common shares subject to repurchase included in accrued expenses and other liabilities			$ 100			$ 100		$ 100
2015 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting period						4 years
Stock options expiration period						10 years
Number of additional shares available for future grant			0			0
2018 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for issuance		3,186,205
Allowed annual percentage increase in shares authorized as percentage of outstanding shares of common stock	4.00%	4.00%
Maximum shares of common stock may be issued		20,887,347
Number of additional shares added to the plan	1,804,670
Number of shares outstanding available for future grant			2,430,357			2,430,357
2018 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for issuance		353,980
Allowed annual percentage increase in shares authorized as percentage of outstanding shares of common stock	1.00%	1.00%
Number of additional shares added to the plan	451,167
Number of shares outstanding available for future grant			1,039,651			1,039,651
Maximum shares allowed to be issued under ESPP		4,778,738
Purchase of common stock through payroll deductions expressed in percentage of fair market value				85.00%
Common stock offering period				6 months
Number of shares issued to the plan						83,848
Aggregate proceeds from shares issued under the plan						$ 900
Stock-based compensation			$ 100		$ 100	100	$ 100
2015 and 2018 Stock Incentive Plans
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense			$ 32,600			$ 32,600
Unrecognized compensation expense estimated to be recognized over period						2 years 7 months 6 days