Note 11 - Net Loss Per Share - Anti-dilutive Securities (Details) - shares	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Antidilutive securities (in shares)	3,522,820	3,310,096
Share-based Payment Arrangement, Option [Member]
Antidilutive securities (in shares)	1,078,813	837,308
Restricted Stock Units (RSUs) [Member]
Antidilutive securities (in shares)	8,200	36,981
Warrant [Member]
Antidilutive securities (in shares)	2,435,807	2,435,807

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 http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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