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Description of Business (Detail) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 12 Months Ended
Jul. 31, 2015
Feb. 28, 2015
Oct. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Organization And Description Of Business [Line Items]          
Entity incorporation state       Delaware  
Entity incorporation date       Aug. 01, 2012  
Net proceeds from sale of common stock       $ 263,434 $ 56,455
Additional paid-in capital       $ 413,725 $ 144,169
IPO          
Organization And Description Of Business [Line Items]          
Common stock, shares issued     5,750,000    
Shares issued, price per share     $ 11.00    
Net proceeds from sale of common stock     $ 56,500    
Preferred stock conversion into common stock     12,298,515    
Additional paid-in capital     $ 74,600    
Follow-on Offering          
Organization And Description Of Business [Line Items]          
Common stock, shares issued 3,980,768 4,147,358      
Shares issued, price per share $ 52.00 $ 18.00      
Net proceeds from sale of common stock $ 193,900 $ 69,500