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Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)
$ in Thousands
6 Months Ended
Jun. 30, 2019
Dec. 31, 2018
Fair Value Disclosures [Abstract]    
Highly liquid marketable securities with original maturities 90 days or less  
Cash equivalents include commercial paper and money market funds $ 32,663 $ 25,543