Common Stock - Summary of Reserved Shares of Common Stock for Future Issuances (Detail) - shares	Dec. 31, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	2,835,101	1,026,674
Stock Compensation Plan [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	1,201,581
Options to purchase common stock [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	1,515,923	607,511
Restricted stock units [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	117,597	419,163