Stock-Based Compensation Expense - Summary of Stock Option Activity (Detail) - Stock Options [Member] $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Shares
Outstanding, Beginning balance (in shares) | shares	4,580,375
Granted (in shares) | shares	1,138,566
Exercised (in shares) | shares	(120,479)
Forfeited/canceled (in shares) | shares	(97,442)
Outstanding, Ending balance (in shares) | shares	5,501,020
Vested and exercisable (in shares) | shares	2,926,282
Vested or expected to vest (in shares) | shares	5,501,020
Weighted Average Exercise Price
Outstanding, Beginning balance (in dollars per share) | $ / shares	$ 8.20
Granted (in dollars per share) | $ / shares	12.93
Exercised (in dollars per share) | $ / shares	6.43
Forfeited/canceled (in dollars per share) | $ / shares	12.10
Outstanding, Ending balance (in dollars per share) | $ / shares	9.15
Vested and exercisable (in dollars per share) | $ / shares	5.91
Vested and expected to vest (in dollars per share) | $ / shares	$ 9.15
Weighted Average Remaining Contractual Life (in years)
Outstanding	7 years 3 months 18 days
Vested and exercisable	5 years 7 months 6 days
Vested and expected to vest	7 years 3 months 18 days
Aggregate Intrinsic Value
Exercised (in dollars) | $	$ 1,000
Outstanding (in dollars) | $	32,817
Vested and exercisable (in dollars) | $	26,759
Vested and expected to vest (in dollars) | $	$ 32,817