Note 6 - Stockholders' Equity - Anti-dilutive Securities (Details) - shares	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Anti-dilutive securities (in shares)	18,416,140	7,992,834
Convertible Debt Securities [Member]
Anti-dilutive securities (in shares)	17,420,222	6,449,950
Warrant, Other [Member]
Anti-dilutive securities (in shares)	653,248	653,248
Share-Based Payment Arrangement, Option [Member]
Anti-dilutive securities (in shares)	342,670	889,636

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration