Summary of Significant Accounting Policies (Net Loss Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net loss available for common shareholders - basic and diluted	$ (4,298)	$ (3,513)	$ (2,769)	$ (3,962)	$ (3,346)	$ (3,355)	$ (3,401)	$ (8,018)	$ (14,542)	$ (18,120)	$ (13,178)
Denominator:
Weighted-average shares outstanding - basic and diluted									46,540	41,599	28,025
Net loss per share - basic and diluted	$ (0.09)	$ (0.07)	$ (0.06)	$ (0.09)	$ (0.08)	$ (0.08)	$ (0.08)	$ (0.23)	$ (0.31)	$ (0.44)	$ (0.47)