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Note 14 - Employee Benefits (Details Textual) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value | $ 185,356 | $ 538,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period | 12,300 | 8,237
Restricted Stock [Member] |  |
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures, Total | 0 |
Employee Stock Option [Member] |  |
Payments For Stock Options Exercised | $ 85,000 | $ 95,000
Restricted Stock Units (RSUs) [Member] |  |
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures, Total | 11,351 | 5,825
Allocated Share-based Compensation Expense, Total | $ 286,000 | $ 196,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options | $ 453,000 |
Retirement Plan [Member] |  |
Defined Contribution Plan Employer Voluntary Matching Bank Contribution | 50.00% | 50.00%
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 | 6 years |
Defined Benefit Plan, Plan Assets, Contributions by Employer | $ 306,000 | $ 258,000
Retirement Plan [Member] | Middlefield Banking Company [Member] |  |
Defined Contribution Plan Annual Vesting Percentage | 20.00% |
Retirement Plan [Member] | Liberty Bank, N.A. [Member] |  |
Deferred Compensation Arrangement with Individual, Requisite Service Period | 3 years |
Directors Retirement Plan [Member] | Middlefield Banking Company [Member] |  |
Deferred Compensation Arrangement with Individual, Requisite Service Period | 5 years |
Retirement Benefits Term | 10 years |
Postretirement Benefits Percentage of Compensation | 25.00% |
Executive Deferred Compensation Plan [Member] | Middlefield Banking Company [Member] |  |
Deferred Compensation Arrangement with Individual, Recorded Liability | $ 504,000 | 912,000
Defined Contribution Plan, Employer Discretionary Contribution Amount | $ 98,000 | $ 110,000
Stock Option and Restricted Stock Plan [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized | 160,000 |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term | 10 years |
Shares, Outstanding, Ending Balance | 7,450 |
The 2017 Plan [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized | 224,000 |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term | 10 years |
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant | 201,708 |
Omnibus Equity Plan [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | 0 | 0
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost, Total | $ 215,000 | $ 0

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