Fair Value Measurements - Level 3 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of liabilities measured at fair value using level 3 significant unobservable inputs (Level 3) on a recurring basis
Beginning balance	$ 379	$ 680
Issuance of common stock warrants	53
Change in the fair value of stock warrants	1,132	(5)
Ending balance	105	379
Common Stock
Reconciliation of liabilities measured at fair value using level 3 significant unobservable inputs (Level 3) on a recurring basis
Issuance of Shares in connection with the settlements	(139)
Series D convertible preferred stock
Reconciliation of liabilities measured at fair value using level 3 significant unobservable inputs (Level 3) on a recurring basis
Issuance of Shares in connection with the settlements	$ (1,320)	(110)
Series C convertible preferred stock
Reconciliation of liabilities measured at fair value using level 3 significant unobservable inputs (Level 3) on a recurring basis
Issuance of Shares in connection with the settlements		$ (186)