Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of shares outstanding, beginning balance	3,134,094	2,086,450
Number of shares, granted	1,585,400	1,352,114
Number of shares, exercised	0	(56,250)
Number of shares, expired	(35,482)	(65,250)
Number of shares, forfeited	(845,964)	(182,970)
Number of shares outstanding, ending balance	3,838,048	3,134,094	2,086,450
Number of shares, exercisable	2,179,198
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average exercise price, outstanding (usd per share), beginning balance	$ 6.23	$ 7.43
Weighted-average exercise price, granted (usd per share)	1.60	4.48
Weighted-average exercise price, exercised (usd per share)	0.00	4.53
Weighted-average exercise price, expired (usd per share)	7.93	10.54
Weighted-average exercise price, forfeited (usd per share)	2.83	5.91
Weighted-average exercise price, outstanding (usd per share), ending balance	5.05	$ 6.23	$ 7.43
Weighted-average exercise price, exercisable (usd per share)	$ 7.11
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average remaining contractual term (in years), outstanding	7 years 2 months	8 years	7 years 2 months
Weighted-average remaining contractual term (in years), exercisable	5 years 7 months
Aggregate intrinsic value, outstanding	$ 0	$ 1,630	$ 0
Aggregate intrinsic value, exercisable	$ 0