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Note 6 - Share-based Payments - Summary of Stock Performance Awards Granted and Amounts Expensed (Details) - Executive Officer [Member] - Stock Performance Awards [Member] - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Compensation Expense Recognized | $ 3,597,000 | $ 2,645,000 | $ 2,007,000
Earned Shares (in shares) | 297,943 |  |
Performance Period 2019 To 2021 [Member] |  |  |
Maximum Shares Subject to Award (in shares) | 83,400 |  |
Target Shares (in shares) | 55,600 |  |
Compensation Expense Recognized | $ 2,168,000 |  |
Performance Period 2018 To 2020 [Member] |  |  |
Maximum Shares Subject to Award (in shares) | 81,000 |  |
Target Shares (in shares) | 54,000 |  |
Compensation Expense Recognized | $ 897,000 | 1,121,000 |
Performance Period 2017 To 2019 [Member] |  |  |
Maximum Shares Subject to Award (in shares) | 89,250 |  |
Target Shares (in shares) | 59,500 |  |
Compensation Expense Recognized | $ 524,000 | 729,000 | 854,000
Earned Shares (in shares) | 69,997 |  |
Performance Period 2016 To 2018 [Member] |  |  |
Maximum Shares Subject to Award (in shares) | 122,250 |  |
Target Shares (in shares) | 81,500 |  |
Compensation Expense Recognized | $ 8,000 | 772,000 | 580,000
Earned Shares (in shares) | 113,298 |  |
Performance Period 2015 To 2017 [Member] |  |  |
Maximum Shares Subject to Award (in shares) | 126,450 |  |
Target Shares (in shares) | 84,300 |  |
Compensation Expense Recognized | $ 0 | $ 23,000 | $ 573,000
Earned Shares (in shares) | 114,648 |  |

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- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. + References 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=116856206&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=116856206&loc=d3e5070-113901 + Details
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- Definition 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. + References 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 + Details
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- Definition Number of shares authorized for issuance 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 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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