Quarterly report pursuant to Section 13 or 15(d)

Organization and Description of Business - Additional Information (Detail)

v3.19.2
Organization and Description of Business - Additional Information (Detail)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2019
USD ($)
Mar. 31, 2019
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Jun. 30, 2019
USD ($)
Segment
Jun. 30, 2018
USD ($)
Dec. 31, 2018
USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]              
Number of operating segments | Segment         1    
Net loss $ (24,038) $ (23,075) $ (17,531) $ (17,005) $ (47,113) $ (34,536)  
Cash flows from operating activities         (46,648) $ (19,264)  
Accumulated deficit (570,177)       (570,177)   $ (523,064)
Cash and cash equivalents and marketable securities $ 241,200       $ 241,200