Note 7 - Embedded Derivatives Liabilities - Schedule of Shares Issued Upon Exercise of Warrants (Details) - $ / shares		3 Months Ended
		Mar. 31, 2021	Dec. 31, 2019
Shares Underlying Warrants (in shares)		150,843	30,377,087
Series F Warrants (in shares)		30,226,244
Series F Warrants [Member]
Warrant, Issuance Date		Apr. 01, 2016
Warrants, Expiration date		Apr. 01, 2021
Warrant Exercise Price (in dollars per share)		$ 40
Shares Underlying Warrants (in shares)		14,041	25,733
Series F Warrants (in shares)		11,692
Series I Warrants [Member]
Warrant, Issuance Date		Sep. 13, 2016
Warrants, Expiration date		Sep. 13, 2021
Warrant Exercise Price (in dollars per share)		$ 220
Shares Underlying Warrants (in shares)		35,368	35,368
Series F Warrants (in shares)
Series K Warrants [Member]
Warrant, Issuance Date		Feb. 17, 2017
Warrants, Expiration date		Feb. 17, 2022
Warrant Exercise Price (in dollars per share)		$ 2
Shares Underlying Warrants (in shares)		7,326	315,986
Series F Warrants (in shares)		308,660
The Series 2020 A Warrants [Member]
Warrant, Issuance Date	[1]	Jul. 06, 2020
Warrants, Expiration date	[1]	Jul. 06, 2025
Warrant Exercise Price (in dollars per share)	[1]	$ 0.60
Shares Underlying Warrants (in shares)	[1]	94,108	30,000,000
Series F Warrants (in shares)	[1]	29,905,892

[1] The Series 2020-A Warrants are equity-classified warrants.