Quarterly report pursuant to Section 13 or 15(d)

Organization and Description of Business - Additional Information (Detail)

v3.19.3
Organization and Description of Business - Additional Information (Detail)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2019
USD ($)
Jun. 30, 2019
USD ($)
Mar. 31, 2019
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Sep. 30, 2019
USD ($)
Segment
Sep. 30, 2018
USD ($)
Dec. 31, 2018
USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]                  
Number of operating segments | Segment             1    
Net loss $ (26,282) $ (24,038) $ (23,075) $ (18,563) $ (17,531) $ (17,005) $ (73,395) $ (53,099)  
Cash flows from operating activities             (69,775) $ (35,341)  
Accumulated deficit (596,459)           (596,459)   $ (523,064)
Cash and cash equivalents and marketable securities $ 218,600           $ 218,600