Note 11 - Warrant Liability - Outstanding Warrant Liability (Details) - USD ($) shares in Thousands	Dec. 31, 2019	Aug. 13, 2019	Aug. 08, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares (in shares)	8,588			544	544	565
The 2011 Warrants [Member]
Shares (in shares)	35
Warrant liability	$ 15,000
October 2015 Warrants [Member]
Shares (in shares)	38
Warrant liability	$ 19,000
Warrant Liability, Current [Member]
Shares (in shares)	73
Warrant liability	$ 34,000
The 2019 Domestic Warrants [Member]
Shares (in shares)	4,199
Warrant liability	$ 2,410,000	$ 3,100,000	$ 3,100,000
The 2019 Foreign Warrants [Member]
Shares (in shares)	2,700
Warrant liability	$ 1,550,000	2,000,000	$ 2,000,000
The 2019 Ladenburg Warrants [Member]
Shares (in shares)	168
Warrant liability	$ 95,000	$ 124,000
Warrant Liability, Noncurrent [Member]
Shares (in shares)	7,067
Warrant liability	$ 4,055,000