Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.0.8
Stock Based Compensation - Stock Option Activity Under Equity Incentive Plan (Detail) (USD $)
 6 Months Ended
Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]  
Number of Shares, Outstanding Beginning Balance 6,526,506
Number of Shares, Granted 1,765,250
Number of Shares, Exercised (58,560)
Number of Shares, Forfeitures (72,333)
Number of Shares, Outstanding Ending Balance 8,160,863
Number of Shares, Vested and expected to vest 8,071,025
Number of Shares, Exercisable 4,450,857
Weighted-Average Exercise Price, Outstanding at beginning of period $ 3.66
Weighted-Average Exercise Price, Granted $ 3.79
Weighted-Average Exercise Price, Exercised $ 1.45
Weighted-Average Exercise Price, Forfeitures $ 4.62
Weighted-Average Exercise Price, Outstanding at end of period $ 3.69
Weighted-Average Exercise Price, Vested and expected to vest $ 3.69
Weighted-Average Exercise Price, Exercisable $ 3.04
Weighted-Average Remaining Contractual Term, Outstanding 7 years 8 months 1 day
Weighted-Average Remaining Contractual Term, Vested and expected to vest 7 years 7 months 24 days
Weighted-Average Remaining Contractual Term, Exercisable 6 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding $ 8,434,466
Aggregate Intrinsic Value, Vested and expected to vest 8,412,349
Aggregate Intrinsic Value, Exercisable $ 7,212,989