Quarterly report pursuant to Section 13 or 15(d)

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

v3.7.0.1
Stock Based Compensation - Stock Option Activity Under Equity Incentive Plan (Detail) - USD ($)
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Number of Shares, Outstanding, Beginning Balance 10,941,745  
Number of Shares, Granted 0  
Number of Shares, Exercised 0 0
Number of Shares, Forfeitures (114,264)  
Number of Shares, Outstanding, Ending Balance 10,827,481  
Number of Shares, Vested and expected to vest 10,773,313  
Number of Shares, Exercisable 8,355,859  
Weighted-Average Exercise Price, Outstanding, Beginning Balance $ 3.00  
Weighted-Average Exercise Price, Granted 0  
Weighted-Average Exercise Price, Exercised 0  
Weighted-Average Exercise Price, Forfeitures 1.49  
Weighted-Average Exercise Price, Outstanding, Ending Balance 3.01  
Weighted-Average Exercise Price, Vested and expected to vest 3.02  
Weighted-Average Exercise Price, Exercisable $ 3.44  
Weighted-Average Remaining Contractual Term, Outstanding 5 years 2 months 12 days  
Weighted-Average Remaining Contractual Term, Vested and expected to vest 5 years 2 months 1 day  
Weighted-Average Remaining Contractual Term, Exercisable 4 years 2 months 9 days  
Aggregate Intrinsic Value, Outstanding $ 115,102  
Aggregate Intrinsic Value, Vested and expected to vest 113,582  
Aggregate Intrinsic Value, Exercisable $ 48,103