Note 16 - Warrant liabilities - Fair Value of Warrants (Details)	Mar. 31, 2019 yr	Dec. 31, 2018 yr	Mar. 31, 2018 yr	Jan. 17, 2018 yr
Measurement Input, Share Price [Member] | Investor Warrants [Member]
Fair value of the warrants	1.95	1.34	1.67	3.98
Measurement Input, Share Price [Member] | Placement Agent Warrants [Member]
Fair value of the warrants	1.95	1.34	1.67	3.98
Measurement Input, Expected Term [Member] | Investor Warrants [Member]
Fair value of the warrants	1.3	1.55	2.3	2.5
Measurement Input, Expected Term [Member] | Placement Agent Warrants [Member]
Fair value of the warrants	1.8	2.05	2.8	3
Measurement Input, Risk Free Interest Rate [Member] | Investor Warrants [Member]
Fair value of the warrants	0.0227	0.025	0.0235	0.0222
Measurement Input, Risk Free Interest Rate [Member] | Placement Agent Warrants [Member]
Fair value of the warrants	0.0227	0.025	0.025	0.0239
Measurement Input, Expected Dividend Rate [Member] | Investor Warrants [Member]
Fair value of the warrants
Measurement Input, Expected Dividend Rate [Member] | Placement Agent Warrants [Member]
Fair value of the warrants
Measurement Input, Price Volatility [Member] | Investor Warrants [Member]
Fair value of the warrants	2.16	1.99	1.64	1.58
Measurement Input, Price Volatility [Member] | Placement Agent Warrants [Member]
Fair value of the warrants	1.87	1.76	1.52	1.47
Measurement Input, Exercise Price [Member] | Investor Warrants [Member]
Fair value of the warrants	6.6	6.6	6.6	6.6
Measurement Input, Exercise Price [Member] | Placement Agent Warrants [Member]
Fair value of the warrants	6.6	6.6	6.6	6.6
Measurement Input, Quoted Price [Member] | Investor Warrants [Member]
Fair value of the warrants	1.23	0.78	1.03	2.93
Measurement Input, Quoted Price [Member] | Placement Agent Warrants [Member]
Fair value of the warrants	1.26	0.8	1.06	2.99