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)
$ in Thousands
 1 Months Ended 12 Months Ended
Jul. 24, 2017
USD ($)
ft²
Options
Mar. 31, 2017
USD ($)
Dec. 31, 2017
USD ($)
ft²
shares
Dec. 31, 2016
USD ($)
Other Commitments [Line Items]        
Rent expense     $ 866 $ 588
Building Lease Agreement [Member]        
Other Commitments [Line Items]        
Lease provided area of office space (in square feet) | ft² 38,875      
Office building lease agreement, renewal terms 5 years      
Number of lease renewal options (in leases) | Options 2      
Total minimum lease payments $ 114   $ 10,590  
San Diego [Member]        
Other Commitments [Line Items]        
Lease provided area of office space (in square feet) | ft²     7,965  
Total minimum lease payments     $ 21  
Operating lease agreements expiring     Aug. 31, 2022  
Professional Employer Organization [Member]        
Other Commitments [Line Items]        
Settlement of claim     $ 400  
Chad Steelberg and Ryan Steelberg [Member]        
Other Commitments [Line Items]        
Estimated common stock calculated value   $ 125    
Chad Steelberg [Member]        
Other Commitments [Line Items]        
Share-based compensation arrangement by share-based payment award, shares issued in period | shares     17,807  
Ryan Steelberg [Member]        
Other Commitments [Line Items]        
Annual salary under agreement     $ 350