Quarterly report pursuant to Section 13 or 15(d)

Description of Business (Detail)

v3.19.1
Description of Business (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]    
Entity incorporation state Delaware  
Entity incorporation date Aug. 01, 2012  
Accumulated Deficit $ 593,242 $ 527,349