Note 11 - Warrant Liability - Outstanding Warrant Liability (Details) - USD ($) shares in Thousands	Mar. 31, 2020	Dec. 31, 2019	Aug. 13, 2019	Aug. 08, 2019
Shares (in shares)	8,247	8,588
The 2011 Warrants [Member]
Shares (in shares)	38
Warrant liability	$ 17,000
Warrant Liability, Current [Member]
Shares (in shares)	38
Warrant liability	$ 17,000
The 2019 Domestic Warrants [Member]
Shares (in shares)	4,199
Warrant liability	$ 2,339,000		$ 3,100,000	$ 3,100,000
The 2019 Foreign Warrants [Member]
Shares (in shares)	2,700
Warrant liability	$ 1,504,000		2,000,000	$ 2,000,000
The 2019 Ladenburg Warrants [Member]
Shares (in shares)	168
Warrant liability	$ 92,000		$ 124,000
Warrant Liability, Noncurrent [Member]
Shares (in shares)	7,067
Warrant liability	$ 3,935,000