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Commitments and Contingencies - Additional Information (Detail) - Office Space and Research Facilities Lease - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Commitment And Contingencies [Line Items]    
Operating leases, rent expense $ 232,947 $ 183,615
Lease agreement description The San Diego facility lease agreement included a tenant improvement allowance which provided for the landlord to pay for tenant improvements on behalf of the Company up to $515,000. Based on the terms of this landlord incentive and involvement of the Company in the construction process, the leasehold improvements purchased under the landlord incentive were determined to be property of the Company.  
Lease expiration date Feb. 28, 2022  
Maximum    
Commitment And Contingencies [Line Items]    
Payments for tenant improvements allowance $ 515,000