Fair Value Measurements - Fair Value Hierarchy (Details) - Recurring - Measured at fair value - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 8,949	$ 17,515
Total Assets	8,949	17,515
Liabilities
Warrant liability	10,735	6,034
Derivative liability	1,442	1,735
Total Liabilities	12,177	7,769
Quoted prices in active markets (Level 1)
Assets
Cash and cash equivalents	8,949	17,515
Total Assets	8,949	17,515
Liabilities
Warrant liability	0	0
Derivative liability	0	0
Total Liabilities	0	0
Quoted prices in inactive markets (Level 2)
Assets
Cash and cash equivalents	0	0
Total Assets	0	0
Liabilities
Warrant liability	0	0
Derivative liability	0	0
Total Liabilities	0	0
Significant unobservable inputs (Level 3)
Assets
Cash and cash equivalents	0	0
Total Assets	0	0
Liabilities
Warrant liability	10,735	6,034
Derivative liability	1,442	1,735
Total Liabilities	$ 12,177	$ 7,769