Summary of Significant Accounting Policies Summary of Significant Accounting Policies Computation of Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accounting Policies [Abstract]
Net loss	$ (18,741)	$ (8,617)	$ (46,127)	$ (33,311)
Change in fair value of warrant liability	$ 0	1,907	$ 0	$ (4,544)
Adjusted net loss		$ (10,524)
Weighted average number of shares used in computing net loss per share, basic	16,841,954	13,527,113	16,103,326	13,478,735
Plus: Effect of dilutive potential common shares from warrants		1,190,140
Weighted average number of shares used in computing net loss per share, diluted	16,841,954	14,717,253	16,103,326	13,478,735
Diluted net loss per share	$ (1.11)	$ (0.72)	$ (2.86)	$ (2.47)