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Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 6 Months Ended
Jan. 28, 2015
Jun. 24, 2014
Jan. 31, 2015
Jun. 30, 2015
Jun. 30, 2014
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]          
Entity incorporation date       Nov. 22, 2005  
Proceeds from public offerings, net of commissions and underwriting discounts   $ 102,672   $ 130,044 $ 102,672
Offering costs   $ 2,508      
Underwriting discounts, commissions and offering costs incurred       $ 473 $ 1,418
IPO [Member]          
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]          
Common stock issued   6,900,000      
Common stock issued price per share   $ 16.00      
Follow-on Offering [Member]          
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]          
Common stock issued 3,942,200   3,942,200    
Common stock issued price per share $ 35.00   $ 35.00    
Proceeds from offering, net of commissions and underwriting discounts $ 130,044   $ 130,044    
Underwriting discounts, commissions and offering costs incurred $ 473   $ 473