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Stock-Based Compensation - Summary of ESPP Share Activity (Detail) - shares
3 Months Ended 12 Months Ended
Mar. 31, 2016
Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Available for future purchases,beginning 2,439,489  
Available for future purchases,ending   2,439,489
2009 Employee Stock Purchase Plan [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Available for future purchases,beginning 279,589 307,448
Additional shares reserved under 2009 ESPP 82,084 80,933
Purchases (33,923) (108,792)
Available for future purchases,ending 327,750 279,589