Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies - Additional Information (Detail)

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Commitments and Contingencies - Additional Information (Detail) - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Facilities Operating Leases      
Other Commitments [Line Items]      
Operating lease expense $ 340,000 $ 77,000  
Laboratory Equipment      
Other Commitments [Line Items]      
Property and equipment, gross 237,000   $ 162,000
Accumulated amortization $ 83,000   $ 75,000