Net Loss Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		12 Months Ended										24 Months Ended	147 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007	Dec. 31, 2006	Dec. 31, 2005	Dec. 31, 2004	Dec. 31, 2003	Mar. 31, 2014
Summary of basic and diluted loss per share
Net loss	$ (2,389)	$ (1,071)	$ (6,939)	$ (4,320)	$ (5,364)	$ (8,420)	$ (9,138)	$ (19,431)	$ (13,994)	$ (5,241)	$ (1,459)	$ (511)	$ (116)	$ (77,322)
Net loss available to common shareholders	$ (2,389)	$ (1,071)												$ (80,374)
Weighted average shares of common stock outstanding	18,785,418	3,037,546
Less: Weighted-average shares of unvested common stock		(2,783)
Total weighted-average shares used in computing net loss per share attributed to common stockholders	18,785,418	3,034,763
Basic and diluted loss per share	$ (0.13)	$ (0.35)