Note 10 - Share-based Compensation - Shares Authorized, Available for Future Grant and Outstanding Under Each Plan (Details)	Dec. 31, 2019 shares
Authorized (in shares)	1,650,000
Available (in shares)	1,372,643
Outstanding (in shares)	439,296
The 2016 Plan [Member]
Authorized (in shares)	1,300,000
Available (in shares)	1,188,243
Outstanding (in shares)	71,272
2014 Directors Plan [Member]
Authorized (in shares)	350,000
Available (in shares)	184,400
Outstanding (in shares)	116,724
The 2005 Plan [Member]
Authorized (in shares)
Available (in shares)	0
Outstanding (in shares)	239,300
2004 Directors Plan [Member]
Authorized (in shares)
Available (in shares)	0
Outstanding (in shares)	12,000

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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 (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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