Common Stock (Details) - shares	Mar. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)	12,771,787	8,407,162
Shares underlying outstanding stock options
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)	4,227,990	4,494,889
Shares underlying unvested restricted stock units
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)	488,921	496,131
Shares available for issuance under the 2018 Incentive Award Plan
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)	6,422,345	2,726,225
Shares available for issuance under the 2018 Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)	1,632,531	689,917