Warrants - Summary of Warrant Activity (Details)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Increase (Decrease) in Warrants Outstanding [Roll Forward]
Number of warrants outstanding (shares), beginning balance	6,033,050
Number of warrants exercised during the period (shares)	(90,947)
Number of warrants expired during the period (share)	(275,324)
Number of warrants outstanding (shares), ending balance	5,666,779
Warrants exercise price (usd per share), beginning balance | $ / shares	$ 7.08
Weighted-average exercise price, warrants exercised during the period (usd per share) | $ / shares	6.20
Weighted-average exercise price, warrants expired during the period (usd per share) | $ / shares	6.05
Warrants exercise price (usd per share), ending balance | $ / shares	$ 7.14
Common Stock
Increase (Decrease) in Warrants Outstanding [Roll Forward]
Issuance of shares from cashless warrant exercises (shares)	11,584