Note 17 - Regulatory Capital (Tables)

12 Months Ended

Dec. 31, 2021

Notes Tables

Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block]

	As of December 31, 2021
				Tier 1			Common			Total Risk
	Leverage			Risk Based			Equity Tier 1			Based
The Middlefield Banking Company		9.80	%		12.72	%		12.72	%		13.97	%
Middlefield Banc Corp.		10.02	%		12.96	%		12.18	%		14.21	%
Adequately capitalized ratio		4.00	%		6.00	%		4.50	%		8.00	%
Adequately capitalized ratio plus fully phased-in capital conservation buffer		4.00	%		8.50	%		7.00	%		10.50	%
Well-capitalized ratio (Bank only)		5.00	%		8.00	%		6.50	%		10.00	%

	As of December 31, 2020
				Tier 1			Common			Total Risk
	Leverage			Risk Based			Equity Tier 1			Based
The Middlefield Banking Company		9.45	%		11.47	%		11.47	%		12.68	%
Middlefield Banc Corp.		10.22	%		11.68	%		10.96	%		12.88	%
Adequately capitalized ratio		4.00	%		6.00	%		4.50	%		8.00	%
Adequately capitalized ratio plus fully phased-in capital conservation buffer		4.00	%		8.50	%		7.00	%		10.50	%
Well-capitalized ratio (Bank only)		5.00	%		8.00	%		6.50	%		10.00	%