Commitments and Contingencies - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Loss Contingencies [Line Items]      
Lease expiration term Jun. 30, 2019    
Future minimum payments under operating lease agreements $ 848,000    
Rent expense $ 417,000 $ 393,000 $ 263,000
Eligibility for 401(k) retirement savings plan 90 days    
401(k) retirement savings plan matching contributions $ 0    
President and Chief Executive Officer [Member]      
Loss Contingencies [Line Items]      
Employment agreement start date 2016-04    
Employment agreement expiry date 2020-04    
Annual salary under agreement $ 365,000    
Agreement termination condition 30 days    
Minimum salary period to determine company's obligation under condition 18 months    
Minimum percentage of salary payable to determine company's obligation 50.00%    
Chief Financial Officer [Member]      
Loss Contingencies [Line Items]      
Employment agreement start date 2016-04    
Employment agreement expiry date 2018-04    
Annual salary under agreement $ 205,000    
Agreement termination condition 30 days    
Minimum salary period to determine company's obligation under condition 9 months