Annual report pursuant to Section 13 and 15(d)

Organization and Description of Business - Additional Information (Detail)

v3.10.0.1
Organization and Description of Business - Additional Information (Detail)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Sep. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2018
USD ($)
Segment
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]                      
Number of operating segments | Segment                 1    
Net loss $ (19,449) $ (18,563) $ (17,531) $ (17,005) $ (5,043) $ (8,234) $ (8,929) $ (5,351) $ (72,548) $ (27,557) $ (26,671)
Cash flows from operating activities                 (54,936) (19,632) $ (23,353)
Accumulated deficit (523,064)       $ (450,516)       (523,064) $ (450,516)  
Cash and cash equivalents and marketable securities $ 178,700               $ 178,700