Note 5 - Allowance for Credit Losses (Details Textual) - USD ($)	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Jan. 01, 2023	Dec. 31, 2022
Financing Receivable, Nonaccrual, Interest Income	$ 2,800,000	$ 57,792
Financing Receivable, Excluding Accrued Interest, Nonaccrual, Modified	364,000	315,000
Off-Balance-Sheet, Credit Loss, Liability	287,000	1,009,000	$ (0)	$ 0
Other Liabilities [Member]
Off-Balance-Sheet, Credit Loss, Liability	$ 287,000	$ 1,000,000

Amortized cost of financing receivable on nonaccrual status that has been modified for debtor experiencing financial difficulty.

No definition available.

+ Details

Name:	mnsb_FinancingReceivableExcludingAccruedInterestNonaccrualModified
Namespace Prefix:	mnsb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of interest income on financing receivable on nonaccrual status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

Name:	us-gaap_FinancingReceivableNonaccrualInterestIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482454/460-10-45-1

+ Details

Name:	us-gaap_OffBalanceSheetCreditLossLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: