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Nature of Business - Additional Information (Detail) - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]    
Cash, cash equivalents, and marketable securities $ 109,800  
Restricted cash 1,097 $ 1,097
Accumulated deficit $ (132,711) $ (119,765)