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Note 14 - Employee Benefits (Details Textual) - USD ($) |  | 12 Months Ended
--- | --- | ---
May 10, 2017 | Dec. 31, 2024 | Dec. 31, 2023
Share-Based Payment Arrangement, Expense |  | $ 714,000 | $ 391,000
Share-Based Payment Arrangement, Expense, Tax Benefit |  | 150,000 | 82,000
Deferred Compensation Share-Based Arrangements, Liability, Current and Noncurrent |  | $ 462,000 | $ 758,000
Share-Based Payment Arrangement, Nonemployee [Member] |  |  |
Shares Issued, Shares, Share-Based Payment Arrangement, before Forfeiture (in shares) |  | 6,768 | 7,475
Shares Issued, Value, Share-Based Payment Arrangement, before Forfeiture |  | $ 187,000 | $ 203,000
Restricted Stock [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (Year) |  | 2 years 4 months 24 days |
Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture (in shares) |  | 70,538 | 36,173
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares) |  | 19,745 | 10,713
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) |  | $ 22.98 | $ 27.57
Share-Based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount |  | $ 1,800,000 |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year) |  | 2 years 1 month 6 days |
Restricted Stock [Member] | Vested in Stock [Member] |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period (in shares) |  | 311,000 | 195,000
Restricted Stock [Member] | Vested in Cash [Member] |  |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value |  | $ 213,000 | $ 114,000
Retirement Plan [Member] |  |  |
Defined Contribution Plan Employer Voluntary Matching Bank Contribution |  | 66.00% | 66.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay |  | 6.00% | 6.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year) |  | 6 years |
Defined Benefit Plan, Plan Assets, Contributions by Employer |  | $ 520,000 | $ 641,000
Retirement Plan [Member] | Middlefield Banking Company [Member] |  |  |
Defined Contribution Plan Annual Vesting Percentage |  | 20.00% |
Executive Deferred Compensation Plan [Member] | Middlefield Banking Company [Member] |  |  |
Deferred Compensation Arrangement with Individual, Recorded Liability |  | $ 3,500,000 | 3,800,000
Defined Contribution Plan, Employer Discretionary Contribution Amount |  | $ 91,000 | $ 437,000
The 2017 Plan [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares) | 448,000 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (Year) | 10 years |  |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares) |  | 352,063 |

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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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