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Stock-Based Compensation - Summary of ESPP Share Activity (Detail) - 2009 Employee Stock Purchase Plan [Member]
3 Months Ended
Mar. 31, 2016
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Available for future purchases, January 1, 2016 279,589
Additional shares reserved under 2009 ESPP 82,084
Purchases (33,923)
Available for future purchases, March 31, 2016 327,750