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 $)
 3 Months Ended
Mar. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]  
Number of Shares, Outstanding Beginning Balance 6,526,506
Number of Shares, Granted 175,000
Number of Shares, Exercised (39,352)
Number of Shares, Forfeitures (5,937)
Number of Shares, Outstanding Ending Balance 6,656,217
Number of Shares, Vested and expected to vest 6,617,299
Number of Shares, Exercisable 4,077,685
Weighted-Average Exercise Price, Outstanding at beginning of period $ 3.66
Weighted-Average Exercise Price, Granted $ 4.97
Weighted-Average Exercise Price, Exercised $ 1.40
Weighted-Average Exercise Price, Forfeitures $ 6.18
Weighted-Average Exercise Price, Outstanding at end of period $ 3.71
Weighted-Average Exercise Price, Vested and expected to vest $ 3.70
Weighted-Average Exercise Price, Exercisable $ 2.93
Weighted-Average Remaining Contractual Term, Outstanding 7 years 5 months 5 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest 7 years 5 months 1 day
Weighted-Average Remaining Contractual Term, Exercisable 6 years 9 months 11 days
Aggregate Intrinsic Value, Outstanding $ 10,708,746
Aggregate Intrinsic Value, Vested and expected to vest 10,701,253
Aggregate Intrinsic Value, Exercisable $ 9,204,627