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Common Stock and Warrants - Additional Information (Detail) - USD ($)
 1 Months Ended 2 Months Ended 12 Months Ended
Nov. 12, 2015
Jul. 31, 2015
Jul. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Class Of Stock [Line Items]            
Common stock, shares outstanding       38,598,618 38,446,000  
Proceeds from issuance of common stock, net         $ 183,897,000  
Warrants outstanding       0 0  
Number of warrants exercised during period         383,000 11,000
Common Stock            
Class Of Stock [Line Items]            
Issuance of common stock, (in shares)         7,353,000  
IPO | Common Stock            
Class Of Stock [Line Items]            
Issuance of common stock, (in shares)   5,227,273        
Public offering net price per share   $ 27.50 $ 27.50      
Net proceeds from offering   $ 134,900,000        
Over-Allotment Option | Common Stock            
Class Of Stock [Line Items]            
Issuance of common stock, (in shares)   681,818        
Cowen            
Class Of Stock [Line Items]            
Issuance of common stock, (in shares)     2,125,439 0    
Proceeds from issuance of common stock, net     $ 49,000,000      
Maximum | Cowen            
Class Of Stock [Line Items]            
Common stock sales agreement aggregate sales proceeds $ 90,000,000          
Commission on gross sales proceeds of common stock 3.00%