Share Based Compensation - Summary of Stock Option Activity (Detail)	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
Stockholders Equity Note [Abstract]
Number of Shares Outstanding, Beginning Balance | shares	11,313,909
Number of Shares Granted | shares	2,975,667
Number of Shares Exercised | shares	(1,062,693)
Number of Shares Cancelled/Forfeited | shares	(833,033)
Number of Shares Outstanding, Ending Balance | shares	12,393,850
Number of Shares Exercisable, Ending Balance | shares	8,043,282
Weighted Average Exercise Price Outstanding, Beginning Balance | $ / shares	$ 1.84
Weighted Average Exercise Price Granted | $ / shares	2.67
Weighted Average Exercise Price Exercised | $ / shares	1.57
Weighted Average Exercise Price Cancelled/Forfeited | $ / shares	2.68
Weighted Average Exercise Price Outstanding, Ending Balance | $ / shares	2.01
Weighted Average Exercise Price Exercisable, Ending Balance | $ / shares	$ 1.93
Weighted Average Remaining Contractual Term (Years) Outstanding, Ending Balance	7 years 3 months 18 days
Weighted Average Remaining Contractual Term (Years) Exercisable, Ending Balance	6 years 2 months 12 days
Aggregate Intrinsic Value Outstanding, Ending Balance | $	$ 15,631,780
Aggregate Intrinsic Value Exercisable, Ending Balance | $	$ 10,880,581