Share-Based Payments - Summary of Stock Option Activity and Related Information (Detail)	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Shares
Outstanding at beginning of period (in shares) | shares	2,024,468
Granted (in shares) | shares	248,025
Exercised (in shares) | shares	(140,400)
Cancelled or forfeited (in shares) | shares	(166,887)
Outstanding at end of period (in shares) | shares	1,965,206
Exercisable at end of period (in shares) | shares	1,161,259
Vested and expected to vest at end of period (in shares) | shares	1,965,206
Weighted-Average Exercise Price
Outstanding at beginning of period (in USD per share) | $ / shares	$ 4.41
Granted (in USD per share) | $ / shares	1.85
Exercised (in USD per share) | $ / shares	0.28
Cancelled or forfeited (in USD per share) | $ / shares	9.85
Outstanding at end of period (in USD per share) | $ / shares	3.92
Exercisable at end of period (in USD per share) | $ / shares	4.51
Vested and expected to vest at end of period (in USD per share) | $ / shares	$ 3.92