Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - Estimate of Fair Value Measurement - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 14,670	$ 17,515
Total Assets	14,670	17,515
Warrant liability	1,073	6,034
Derivative liability	3,136	1,735
Total Liabilities	4,209	7,769
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	14,670	17,515
Total Assets	14,670	17,515
Warrant liability	0	0
Derivative liability	0	0
Total Liabilities	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total Assets	0	0
Warrant liability	0	0
Derivative liability	0	0
Total Liabilities	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total Assets	0	0
Warrant liability	1,073	6,034
Derivative liability	3,136	1,735
Total Liabilities	$ 4,209	$ 7,769