Fair Value Measurements - Fair Value Hierarchy (Details) - Recurring - Measured at fair value - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 20,560	$ 17,515
Total Assets	20,560	17,515
Liabilities
Warrant liability	6,039	6,034
Derivative liability	2,047	1,735
Total Liabilities	8,086	7,769
Quoted prices in active markets (Level 1)
Assets
Cash and cash equivalents	20,560	17,515
Total Assets	20,560	17,515
Liabilities
Warrant liability	0	0
Derivative liability	0	0
Total Liabilities	0	0
Fair Value, Inputs, Level 2 [Member]
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	6,039	6,034
Derivative liability	2,047	1,735
Total Liabilities	$ 8,086	$ 7,769