Note 11 - Shareholders' Equity - Summary of Certain Additional Information About Stock Options (Details) - Share-based Payment Arrangement, Option [Member] - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Weighted average grant-date fair value for options granted during the year (in dollars per share)	$ 1.08	$ 1.33
Vested options in-the-money (in shares)	71,993	344
Aggregate intrinsic value of options exercised during the year	$ 1

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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 (d)(2)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration