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 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Other Commitments [Line Items]          
Property and equipment, net $ 963,000   $ 963,000   $ 334,000
Facilities          
Other Commitments [Line Items]          
Operating lease expense 182,000 $ 57,000 387,000 $ 187,000  
Laboratory Equipment          
Other Commitments [Line Items]          
Property and equipment, net 171,000   171,000   136,000
Accumulated amortization $ 66,000   $ 66,000   $ 44,000