Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Detail) - shares	Mar. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	7,606,865	6,039,105
Restricted Stock [Member]
Class of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	20,168	30,252
Employee Stock Option [Member]
Class of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	5,310,482	3,414,445
Restricted Stock Units [Member]
Class of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	1,630	2,300
2018 Stock Option and Incentive Plan [Member]
Class of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	202,260	332,513
2018 Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	776,325	459,595
2019 Inducement Plan [Member]
Class of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	1,296,000	1,800,000