Note 3 - Share-based Compensation Plans - Unrecognized Compensation Cost (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Unrecognized compensation costs	$ 8,252	$ 10,440
Weighted Average years to recognition (Year)	1 year 343 days	1 year 215 days
Restricted Stock Units (RSUs) [Member]
Unrecognized compensation costs	$ 3,969	$ 6,340
Weighted Average years to recognition (Year)	1 year 346 days	1 year 127 days
Performance Stock Units (PSUs) [Member]
Unrecognized compensation costs	$ 4,283	$ 4,100
Weighted Average years to recognition (Year)	1 year 339 days	1 year 350 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

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