Note 12 - Fair Value Measurements - Fair Value of Liabilities on a Recurring Basis (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Warrant liabilities	$ (865)	$ (2,387)
Total warrant liabilities	(865)	(2,387)
Fair Value, Inputs, Level 1 [Member]
Warrant liabilities
Total warrant liabilities
Fair Value, Inputs, Level 2 [Member]
Warrant liabilities
Total warrant liabilities
Fair Value, Inputs, Level 3 [Member]
Warrant liabilities	(865)	(2,387)
Total warrant liabilities	$ (865)	$ (2,387)