Note 8 - Stock-based Compensation (Details Textual) - USD ($)	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019
Incentive Plan [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 749,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	2 years 146 days
Share-based Payment Arrangement, Option [Member]
Share-based Payment Arrangement, Expense	$ 153,000	$ 147,000
Share-based Payment Arrangement, Option [Member] \| Incentive Plan [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	263,000
Restricted Stock [Member]
Share-based Payment Arrangement, Expense	4,000	$ 2,000
Restricted Stock [Member] \| Incentive Plan [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 486,000

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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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.

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