Warrants (Details 2)	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Increase (Decrease) in Warrants Outstanding [Roll Forward]
Beginning balance, number of warrants outstanding (shares)	6,033,050
Number of warrants exercised during the period (shares)	(90,947)
Ending balance, number of warrants outstanding (shares)	5,942,103
Beginning balance, weighted-average exercise price (usd per share) | $ / shares	$ 7.08
Weighted-average exercise price, warrants exercised during the period (usd per share) | $ / shares	(6.20)
Ending balance, weighted-average exercise price (usd per share) | $ / shares	$ 7.09
Common Stock
Increase (Decrease) in Warrants Outstanding [Roll Forward]
Issuance of shares from cashless warrant exercises (shares)	11,584