Quarterly report pursuant to Section 13 or 15(d)

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

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Stock Based Compensation - Stock Option Activity Under Equity Incentive Plan (Detail) - Jun. 30, 2015 - USD ($)
Total
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]  
Number of Shares, Outstanding Beginning Balance 8,168,942
Number of Shares, Granted 2,105,500
Number of Shares, Exercised (61,873)
Number of Shares, Forfeitures (61,333)
Number of Shares, Outstanding Ending Balance 10,151,236
Number of Shares, Vested and expected to vest 10,051,806
Number of Shares, Exercisable 6,032,323
Weighted-Average Exercise Price, Outstanding at beginning of period $ 3.69
Weighted-Average Exercise Price, Granted 4.38
Weighted-Average Exercise Price, Exercised 1.83
Weighted-Average Exercise Price, Forfeitures 4.88
Weighted-Average Exercise Price, Outstanding at end of period 3.83
Weighted-Average Exercise Price, Vested and expected to vest 3.83
Weighted-Average Exercise Price, Exercisable $ 3.41
Weighted-Average Remaining Contractual Term, Outstanding 7 years 3 months 29 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest 7 years 3 months 22 days
Weighted-Average Remaining Contractual Term, Exercisable 6 years 2 months 27 days
Aggregate Intrinsic Value, Outstanding $ 8,726,000
Aggregate Intrinsic Value, Vested and expected to vest 8,714,000
Aggregate Intrinsic Value, Exercisable $ 8,158,000