Quarterly report pursuant to Section 13 or 15(d)

Description of Business (Detail)

v3.19.3
Description of Business (Detail) - USD ($)
$ in Thousands
9 Months Ended
Sep. 30, 2019
Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]    
Entity incorporation state DE  
Entity incorporation date Aug. 01, 2012  
Accumulated Deficit $ 739,465 $ 527,349