Share-Based Payments - Summary of Stock Option Activity and Related Information (Detail) - $ / shares	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Shares
Outstanding at beginning of period	1,438,528
Granted	744,328
Exercised	(67,914)
Cancelled or forfeited	(54,608)
Outstanding at end of period	2,060,334	1,438,528
Exercisable at June 30, 2015	740,977
Vested and expected to vest at June 30, 2015	1,733,902
Weighted-Average Exercise Price
Outstanding at beginning of period (in USD per share)	$ 4.93
Granted (in USD per share)	9.05
Exercised (in USD per share)	0.80
Cancelled or forfeited (in USD per share)	7.77
Outstanding at end of period (in USD per share)	6.48	$ 4.93
Exercisable at end of period (in USD per share)	4.68
Vested and expected to vest at end of period	$ 6.90
Remaining Contractual Life (in years)
Outstanding at beginning of period	8 years 2 months 1 day	7 years 10 months 10 days
Exercisable at June 30, 2015	7 years 4 months 2 days
Vested and expected to vest at June 30, 2015	8 years 4 months 10 days