Note 4 - Stock-based Compensation - Unamortized Compensation Expense (Details)	12 Months Ended
Dec. 31, 2019 USD ($)
Share-based Payment Arrangement, Option [Member]
Stock Options, unamortized expense	$ 7,989,431
Stock Options, weighted average remaining recognition period (Year)	2 years 255 days
Restricted Stock Units (RSUs) [Member]
Stock Options, unamortized expense	$ 221,462
Stock Options, weighted average remaining recognition period (Year)	2 years 226 days

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration