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Employee Stock Purchase Plan - Additional Information (Detail) - Totals - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Aug. 16, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Percentage of lower limit value of common stock     85.00%    
Purchase period     6 months    
Maximum limit of payroll deductions (percent)     10.00%    
Number of shares issue that the ESPP authorizes for purchase by eligible employees         1,500,132
Total fair value of awards recognized as expenses $ 100,000 $ 26,000 $ 300,000 $ 26,000