Regulatory Capital Requirements (Tables)

12 Months Ended

Dec. 31, 2020

Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]

Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations

The following table presents BMBC's and the Bank’s regulatory capital ratios and the minimum capital requirements for the Bank to be considered “Well Capitalized” by regulators as of December 31, 2020 and 2019:

	Actual				Minimum to be Well Capitalized
(dollars in thousands)	Amount		Ratio		Amount		Ratio
December 31, 2020
Total capital to risk weighted assets:
BMBC	$	583,057	15.55	%	$	375,045	10.00	%
Bank	$	477,792	12.75	%	$	374,758	10.00	%
Tier I capital to risk weighted assets:
BMBC	$	444,640	11.86	%	$	300,036	8.00	%
Bank	$	432,258	11.53	%	$	299,807	8.00	%
Common equity Tier I risk weighted assets:
BMBC	$	423,475	11.29	%	$	243,779	6.50	%
Bank	$	432,258	11.53	%	$	243,593	6.50	%
Tier I leverage ratio (Tier I capital to total quarterly average assets):
BMBC	$	444,640	9.04	%	$	246,002	5.00	%
Bank	$	432,258	8.79	%	$	245,837	5.00	%
December 31, 2019
Total capital to risk weighted assets:
BMBC	$	547,440	14.69	%	$	372,690	10.00	%
Bank	$	450,212	12.09	%	$	372,435	10.00	%
Tier I capital to risk weighted assets:
BMBC	$	425,773	11.42	%	$	298,152	8.00	%
Bank	$	427,250	11.47	%	$	297,948	8.00	%
Common equity Tier I to risk weighted assets:
BMBC	$	404,715	10.86	%	$	242,249	6.50	%
Bank	$	427,250	11.47	%	$	242,083	6.50	%
Tier I leverage ratio (Tier I capital to total quarterly average assets):
BMBC	$	425,773	9.33	%	$	228,216	5.00	%
Bank	$	427,250	9.37	%	$	227,997	5.00	%