Share-Based Payments - Summary of Stock Option Activity and Related Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
Outstanding at beginning of period (in shares)	1,803,574
Granted (in shares)	1,747,495
Exercised (in shares)	(656,532)
Cancelled or forfeited (in shares)	(870,069)
Outstanding at end of period (in shares)	2,024,468	1,803,574
Exercisable at end of period (in shares)	1,139,514
Vested and expected to vest at end of period (in shares)	1,879,868
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 6.28
Granted (in dollars per share)	1.69
Exercised (in dollars per share)	0.41
Cancelled or forfeited (in dollars per share)	5.86
Outstanding at end of period (in dollars per share)	4.41	$ 6.28
Exercisable at end of period (in dollars per share)	5.09
Vested and expected to vest at end of period (in dollars per share)	$ 4.49
Remaining Contractual Life (in years)
Remaining contractual life of stock options outstanding	8 years 8 months 22 days	7 years 9 months 10 days
Exercisable at end of period	8 years 30 days
Vested and expected to vest at end of period	8 years 7 months 28 days
Outstanding intrinsic value beginning of period	$ 841	$ 1,540
Aggregate intrinsic value exercisable (in US dollars)	779
Total intrinsic value of options vested and expected to vest	$ 834