Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies - Additional Information (Detail)

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Commitments and Contingencies - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Other Commitments [Line Items]    
Property and equipment, net $ 1,952,000 $ 334,000
Accumulated amortization 412,000 269,000
Facilities    
Other Commitments [Line Items]    
Operating lease expense 625,000,000 288,000,000
Laboratory Equipment    
Other Commitments [Line Items]    
Property and equipment, net 162,000 136,000
Accumulated amortization $ 75,000 $ 44,000