Fair Value Measurements (Details) - Recurring [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Cash equivalents	$ 67,374	$ 20,673
Short-term investments		35,035
Warrant liability	(878)	(693)
Level I [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Cash equivalents	67,374	20,673
Short-term investments		35,035
Warrant liability	0	0
Level II [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Cash equivalents	0	0
Short-term investments		0
Warrant liability	0	0
Level III [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Cash equivalents	0	0
Short-term investments		0
Warrant liability	(878)	$ (693)
Unrealized loss recognized	$ (200)