Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Stock Option Activity Under Equity Incentive Plan (Detail)

v2.4.0.6
Stock Based Compensation - Stock Option Activity Under Equity Incentive Plan (Detail) (USD $)
9 Months Ended
Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of Shares, Outstanding at December 31, 2011 3,672,179
Number of Shares, Granted 1,787,000
Number of Shares, Exercised (330,352)
Number of shares, Forfeitures   
Number of Shares, Outstanding at September 30, 2012 5,128,827
Number of Shares, Vested and expected to vest September 30, 2012 5,068,823
Number of Shares, Exercisable at September 30, 2012 2,089,451
Weighted-Average Exercise Price, Outstanding at December 31, 2011 $ 1.45
Weighted-Average Exercise Price, Granted $ 6.28
Weighted-Average Exercise Price, Exercised $ 1.36
Weighted-Average Exercise Price, Forfeitures   
Weighted-Average Exercise Price, Outstanding at September 30, 2012 $ 3.14
Weighted-Average Exercise Price, Vested and expected to vest September 30, 2012 $ 3.12
Weighted-Average Exercise Price, Exercisable at September 30, 2012 $ 1.78
Weighted-Average Remaining Contractual Term, Outstanding at September 30, 2012 8 years 2 months 27 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest September 30, 2012 8 years 2 months 23 days
Weighted-Average Remaining Contractual Term, Exercisable at September 30, 2012 7 years 2 months 27 days
Aggregate Intrinsic Value, Outstanding at September 30, 2012 $ 21,102,085
Aggregate Intrinsic Value, Vested and expected to vest September 30, 2012 20,964,921
Aggregate Intrinsic Value, Exercisable at September 30, 2012 $ 11,398,737