Summary of Significant Accounting Policies - Summary of Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ 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
Calculation of net loss and the number of shares used to compute basic and diluted earnings per share [Abstract]
Net loss – basic		$ (5,095)	$ (2,422)	$ (3,699)	$ (3,488)	$ (2,945)	$ (4,558)	$ (4,600)	$ (5,278)	$ (14,704)		$ (17,381)		$ (30,324)
Adjust for gain on warrant derivative liability														(1,835)
Net loss - diluted										$ (14,704)		$ (17,381)		$ (32,159)
Net loss per share – basic						$ (0.31)	$ (0.48)	$ (0.49)	$ (0.57)	$ (0.91)	[1]	$ (1.84)	[1]	$ (4.81)	[1]
Weighted average shares outstanding – basic	[1]									16,161,687		9,452,050		6,300,614
Potentially dilutive warrant exercises														268,397
Weighted average shares outstanding – diluted	[1]									16,161,687		9,452,050		6,569,011
Net loss per share – diluted						$ (0.31)	$ (0.48)	$ (0.52)	$ (0.57)	$ (0.91)	[1]	$ (1.84)	[1]	$ (5.10)	[1]

[1] Reflects a one-for-sixteen (1:16) reverse stock split effected on April 8, 2014.