Stock-Based Compensation (Details 3) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Number of shares
Outstanding at beginning of period (in shares)	2,086,450
Granted (in shares)	1,352,114
Exercised (shares)	(56,250)
Forfeited (in shares)	(178,970)
Expired (in shares)	(12,000)
Outstanding at end of period (in shares)	3,191,344	2,086,450
Exercisable at end of period (in shares)	1,469,897
Weighted-average exercise price
Outstanding at beginning of period (in dollars per share)	$ 7.43
Granted (in dollars per share)	4.48
Exercised (in dollars per share)	4.53
Forfeited (in dollars per share)	5.63
Expired (in dollars per share)	10.50
Outstanding at end of period (in dollars per share)	6.32	$ 7.43
Exercisable at end of period (in dollars per share)	$ 8.81
Additional disclosures
Weighted-average remaining contractual term (in years), Outstanding	8 years 1 month	8 years
Weighted-average remaining contractual term (in years), Exercisable	7 years
Aggregate intrinsic value, Outstanding	$ 602	$ 0
Aggregate intrinsic value, Exercisable	$ 189