Stockholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Aug. 04, 2015
Jul. 29, 2015
Dec. 01, 2014
Jan. 30, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2016
Subsidiary, Sale of Stock [Line Items]              
Common stock, shares authorized         100,000,000   100,000,000
Common stock, par value         $ 0.001   $ 0.001
Preferred stock, shares authorized         5,000,000   5,000,000
Preferred stock, par value         $ 0.001   $ 0.001
Common stock, shares outstanding         27,254,863   27,296,863
Preferred stock, shares issued         0   0
Preferred stock, shares outstanding         0   0
Common stock, shares issued       5,750,000      
Aggregate gross offering proceeds       $ 63,250      
Net proceeds as a result of IPO       56,297   $ 57,762  
Underwriting discounts and commissions       $ 6,953      
Initial Public Offering [Member]              
Subsidiary, Sale of Stock [Line Items]              
Public offering price per share       $ 11.00   $ 11.00  
Net proceeds from offering of common stock           $ 56,297  
Initial Public Offering [Member] | Common Stock [Member]              
Subsidiary, Sale of Stock [Line Items]              
Common stock, shares issued           5,750,000  
Net proceeds from offering of common stock           $ 6  
Private Placement [Member]              
Subsidiary, Sale of Stock [Line Items]              
Public offering price per share           $ 8.74  
Net proceeds from offering of common stock           $ 100  
Private Placement [Member] | Chief Medical Officer [Member]              
Subsidiary, Sale of Stock [Line Items]              
Common stock, shares issued     11,442        
Public offering price per share     $ 8.74        
Gross proceeds of common stock     $ 100        
Private Placement [Member] | Common Stock [Member]              
Subsidiary, Sale of Stock [Line Items]              
Common stock, shares issued           11,442  
Follow On Public Offering [Member]              
Subsidiary, Sale of Stock [Line Items]              
Public offering price per share         $ 18.60    
Net proceeds from offering of common stock $ 75,231       $ 75,231    
Follow On Public Offering [Member] | Common Stock [Member]              
Subsidiary, Sale of Stock [Line Items]              
Common stock, shares issued   3,763,440     4,327,956    
Public offering price per share $ 18.60            
Net proceeds from offering of common stock         $ 4    
Underwriter's Over-Allotment [Member] | Common Stock [Member] | Maximum [Member]              
Subsidiary, Sale of Stock [Line Items]              
Common stock, shares issued 564,516