XML 20 R1.htm IDEA: XBRL DOCUMENT v3.25.0.1
Document And Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2024
Mar. 13, 2025
Jun. 30, 2024
Document Information [Line Items]      
Entity Central Index Key 0000836147    
Entity Registrant Name Middlefield Banc Corp.    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2024    
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2024    
Document Transition Report false    
Entity File Number 001-36613    
Entity Incorporation, State or Country Code OH    
Entity Tax Identification Number 34-1585111    
Entity Address, Address Line One 15985 East High Street    
Entity Address, City or Town Middlefield    
Entity Address, State or Province OH    
Entity Address, Postal Zip Code 44062-0035    
City Area Code 440    
Local Phone Number 632-1666    
Title of 12(b) Security Common Stock, Without Par Value    
Trading Symbol MBCN    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 186,500,000
Entity Common Stock, Shares Outstanding   8,081,302  
Auditor Firm ID 74    
Auditor Name S. R. Snodgrass, P.C    
Auditor Location Cranberry Township, Pennsylvania