Share-Based Payments - Summary of Stock Option Activity and Related Information (Detail)	9 Months Ended
	Sep. 30, 2016 $ / shares shares
Shares
Outstanding at beginning of period (in shares) | shares	1,803,574
Granted (in shares) | shares	1,747,495
Exercised (in shares) | shares	(341,526)
Cancelled or forfeited (in shares) | shares	(494,787)
Outstanding at end of period (in shares) | shares	2,714,756
Exercisable at June 30, 2016 (in shares) | shares	1,606,002
Vested and expected to vest at June 30, 2016 (in shares) | shares	2,530,001
Weighted-Average Exercise Price
Outstanding at beginning of period (in USD per share) | $ / shares	$ 6.28
Granted (in USD per share) | $ / shares	1.69
Exercised (in USD per share) | $ / shares	0.49
Cancelled or forfeited (in USD per share) | $ / shares	3.30
Outstanding at end of period (in USD per share) | $ / shares	4.60
Exercisable at end of period (in USD per share) | $ / shares	5.18
Vested and expected to vest at end of period (in USD per share) | $ / shares	$ 4.69