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Employee Benefits - Additional Information (Detail) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Retirement Plan [Member] |  |  |
Deferred Compensation Arrangement with Individual, Requisite Service Period | 1 year |  |
Defined Contribution Plan, Employer Voluntary Matching, Bank Contribution | 50.00% |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay | 6.00% |  |
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent | 100.00% |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period | 6 years |  |
Defined Benefit Plan, Contributions by Employer | $ 156,000 | $ 143,000 | $ 155,000
Retirement Plan [Member] | Middlefield Banking Company [Member] |  |  |
Defined Contribution Plan Annual Vesting Percentage | 20.00% |  |
Directors Retirement Plan [Member] | Middlefield Banking Company [Member] |  |  |
Deferred Compensation Arrangement with Individual, Requisite Service Period | 5 years |  |
Retirement Benefits Term | 10 years |  |
Post-retirement Benefits Percentage of Compensation | 25.00% |  |
Executive Deferred Compensation Plan [Member] | Middlefield Banking Company [Member] |  |  |
Defined Contribution Plan, Employer Discretionary Contribution Amount | $ 65,000 | $ 115,000 | $ 120,000

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- Definition The percentage of matching voluntary contributions that the bank bases its contributions to the plan on. + References No definition available. + Details
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- Definition Minimum period the individual is required to perform services to be fully vested under the deferred compensation arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6409961&loc=d3e20487-108367 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of contributions made by the employer to defined benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(ii) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 35 -Paragraph 123 -Subparagraph B -URI http://asc.fasb.org/extlink&oid=64937487&loc=d3e36068-114959 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 35 -Paragraph 63 -Subparagraph B -URI http://asc.fasb.org/extlink&oid=64937038&loc=d3e12551-114930 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(iv)(01) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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