Warrants (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Class of Warrant or Right [Line Items]
Warrants exercised via cashless exercises	419,244	13,274
Warrants exercised for cash		313,756
Cash proceeds generated from exercise of warrants	$ 2.1
Shares of common stock issued from exercise of warrants	603,545	9,315
November 21, 2012 Warrants
Class of Warrant or Right [Line Items]
Exercise price of warrants (in dollars per share)	$ 7.86
Number of warrants outstanding	695,383