Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Number of Shares, Outstanding, Beginning balance	19,211
Number of Shares, Granted	3,772
Number of Shares, Exercised	(752)
Number of Shares, Forfeited	(584)
Number of Shares, Outstanding, Ending balance	21,647	19,211
Number of shares vested and expected to vest	21,260
Number of stock option exercisable	15,797
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 5.72
Weighted Average Exercise Price, Granted	5.61
Weighted Average Exercise Price, Exercised	3.45
Weighted Average Exercise Price, Forfeited	7.05
Weighted Average Exercise Price, Outstanding, Ending balance	5.75	$ 5.72
Weighted average exercise price of shares vested and expected to vest (in dollars per share)	5.73
Weighted average exercise price for exercisable option (in dollars per share)	$ 5.31
Weighted Average Remaining Contractual Term	6 years 4 months 17 days	6 years 2 months 27 days
Weighted Average Remaining Contractual Term, Vested and expected to vest	6 years 3 months 26 days
Weighted Average Remaining Contractual Term, Exercisable	5 years 4 months 13 days
Aggregate Intrinsic Value, Outstanding	$ 16,475	$ 47,963
Aggregate Intrinsic Value, Vested and expected to vest	16,470
Aggregate Intrinsic Value, Exercisable	$ 16,224