Warrants (Details)				3 Months Ended
	Mar. 31, 2015	Mar. 31, 2015 April 4, 2011 Warrants	Apr. 04, 2011 April 4, 2011 Warrants	Mar. 31, 2015 November 21, 2012 Warrants	Nov. 21, 2012 November 21, 2012 Warrants
Class of Warrant or Right [Line Items]
Exercise price of warrants (in dollars per share)		6.74	7.46	7.86	8.70
Number of warrants outstanding	2,452,439	1,384,647		1,067,792
Warrants exercised				13,274
Shares of common stock issued				9,315