Fair Value Measurements (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Increase in fair value of warrant liability	$ 6,000
Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Cash equivalents	56,972	$ 20,673
Short-term investments		35,035
Warrant liability	(6,686)	(693)
Level I [Member] | Recurring [Member]
Fair value measurements by level for assets and liabilities measured at fair value on a recurring basis [Abstract]
Cash equivalents	56,972	20,673
Short-term investments		35,035
Warrant liability	0	0
Level II [Member] | Recurring [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] | Recurring [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	$ (6,686)	$ (693)