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, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 12,290	$ 14,670
Total Assets	12,290	14,670
Warrant liability	152	1,073
Derivative liability	1,474	3,136
Total Liabilities	1,626	4,209
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	12,290	14,670
Total Assets	12,290	14,670
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 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 equivalents	0	0
Total Assets	0	0
Warrant liability	152	1,073
Derivative liability	1,474	3,136
Total Liabilities	$ 1,626	$ 4,209