Note 18 - Warrant Liabilities - Warrant Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Jan. 17, 2018
Proceeds allocated to warrant liabilities	$ 255	$ 826	$ 255	$ 826	$ 135	$ 606	$ 1,327	$ 2,275
Change in fair value of warrants	120	(501)	(351)	(1,449)
Investor Warrants [Member]
Proceeds allocated to warrant liabilities	200	684	200	684	32	503	1,103	1,890
Change in fair value of warrants	168	(419)	(303)	(1,206)
Placement Agent Warrants [Member]
Proceeds allocated to warrant liabilities	55	142	55	142	$ 103	$ 103	$ 224	$ 385
Change in fair value of warrants	$ (48)	$ (82)	$ (48)	$ (243)