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Stockholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 6 Months Ended
Jan. 28, 2015
Jan. 31, 2015
Jun. 30, 2015
Jun. 30, 2014
Underwriting discounts, commissions and offering costs incurred     $ 473 $ 1,418
Follow-on Offering [Member]        
Common stock issued 3,942,200 3,942,200    
Common stock issued price per share $ 35.00 $ 35.00    
Shares issued related to the exercise of over allotment option by underwriters   514,200    
Proceeds from offering, net of commissions and underwriting discounts $ 130,044 $ 130,044    
Underwriting discounts, commissions and offering costs incurred $ 473 $ 473