Loans and Allowance for Credit Losses - Summary of Loans by Year of Origination (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2026	Dec. 31, 2025
Total Loans
2026/2025	$ 41,858	$ 172,345
2025/2024	174,400	127,543
2024/2023	117,757	124,675
2023/2022	117,476	167,162
2022/2021	161,854	130,332
Prior	460,494	348,320
Revolving Loans Amortized Cost Basis	83,998	91,883
Total	1,157,837	1,162,260
Total Gross Charge Offs
2026/2025	0	243
2025/2024	0	4
2024/2023	9	19
2023/2022	22	114
2022/2021	60	23
Prior	38	102
Revolving Loans Amortized Cost Basis	18	64
Total	147	569
Real Estate:
Total Gross Charge Offs
2026/2025	0	25
2025/2024	0	0
2024/2023	0	0
2023/2022	0	19
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	0	44
Real Estate: \| Residential
Total Loans
2026/2025	15,603	19,106
2025/2024	19,262	15,378
2024/2023	15,060	31,429
2023/2022	30,620	44,627
2022/2021	44,080	38,637
Prior	186,445	156,978
Revolving Loans Amortized Cost Basis	19,691	23,082
Total	330,761	329,237
Total Gross Charge Offs
2026/2025	0	25
2025/2024	0	0
2024/2023	0	0
2023/2022	0	0
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	0	25
Real Estate: \| Commercial
Total Loans
2026/2025	13,602	99,359
2025/2024	98,158	77,144
2024/2023	71,155	55,898
2023/2022	52,300	69,488
2022/2021	68,475	81,953
Prior	242,490	166,212
Revolving Loans Amortized Cost Basis	3,849	2,126
Total	550,029	552,180
Total Gross Charge Offs
2026/2025	0	0
2025/2024	0	0
2024/2023	0	0
2023/2022	0	19
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	0	19
Real Estate: \| Construction
Total Loans
2026/2025	3,623	11,170
2025/2024	15,336	12,220
2024/2023	9,799	7,561
2023/2022	8,174	7,446
2022/2021	7,441	0
Prior	7,021	7,022
Revolving Loans Amortized Cost Basis	0	0
Total	51,394	45,419
Total Gross Charge Offs
2026/2025	0	0
2025/2024	0	0
2024/2023	0	0
2023/2022	0	0
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	0	0
Commercial and Industrial
Total Loans
2026/2025	8,759	41,919
2025/2024	40,925	22,270
2024/2023	21,296	20,315
2023/2022	17,681	6,442
2022/2021	5,850	2,670
Prior	12,173	10,345
Revolving Loans Amortized Cost Basis	51,010	57,120
Total	157,694	161,081
Total Gross Charge Offs
2026/2025	0	218
2025/2024	0	0
2024/2023	0	0
2023/2022	0	0
2022/2021	0	0
Prior	0	5
Revolving Loans Amortized Cost Basis	0	0
Total	0	223
Consumer
Total Loans
2026/2025	209	688
2025/2024	620	411
2024/2023	342	5,635
2023/2022	4,866	17,322
2022/2021	14,338	7,072
Prior	8,015	3,311
Revolving Loans Amortized Cost Basis	8,330	8,437
Total	36,720	42,876
Total Gross Charge Offs
2026/2025	0	0
2025/2024	0	4
2024/2023	9	19
2023/2022	22	95
2022/2021	60	23
Prior	38	97
Revolving Loans Amortized Cost Basis	18	64
Total	147	302
Other
Total Loans
2026/2025	62	103
2025/2024	99	120
2024/2023	105	3,837
2023/2022	3,835	21,837
2022/2021	21,670	0
Prior	4,350	4,452
Revolving Loans Amortized Cost Basis	1,118	1,118
Total	31,239	31,467
Total Gross Charge Offs
2026/2025	0	0
2025/2024	0	0
2024/2023	0	0
2023/2022	0	0
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	0	0
Pass \| Real Estate: \| Residential
Total Loans
2026/2025	15,603	18,321
2025/2024	18,479	15,378
2024/2023	15,060	29,290
2023/2022	28,507	43,086
2022/2021	42,478	38,637
Prior	185,828	156,386
Revolving Loans Amortized Cost Basis	19,691	23,082
Total	325,646	324,180
Pass \| Real Estate: \| Commercial
Total Loans
2026/2025	13,602	98,535
2025/2024	97,337	69,669
2024/2023	65,662	55,379
2023/2022	52,300	69,488
2022/2021	68,475	74,487
Prior	229,772	164,948
Revolving Loans Amortized Cost Basis	3,849	2,126
Total	530,997	534,632
Pass \| Real Estate: \| Construction
Total Loans
2026/2025	3,623	11,170
2025/2024	15,336	12,220
2024/2023	9,799	6,807
2023/2022	7,362	7,446
2022/2021	7,441	0
Prior	7,021	7,022
Revolving Loans Amortized Cost Basis	0	0
Total	50,582	44,665
Pass \| Commercial and Industrial
Total Loans
2026/2025	8,759	40,139
2025/2024	39,221	22,131
2024/2023	21,165	20,315
2023/2022	17,681	6,442
2022/2021	5,850	2,670
Prior	12,063	10,182
Revolving Loans Amortized Cost Basis	51,010	56,820
Total	155,749	158,699
Pass \| Consumer
Total Loans
2026/2025	209	688
2025/2024	620	411
2024/2023	342	5,635
2023/2022	4,866	17,322
2022/2021	14,338	7,047
Prior	7,926	3,229
Revolving Loans Amortized Cost Basis	8,330	8,437
Total	36,631	42,769
Pass \| Other
Total Loans
2026/2025	62	103
2025/2024	99	120
2024/2023	105	3,837
2023/2022	3,835	21,837
2022/2021	21,670	0
Prior	4,350	4,452
Revolving Loans Amortized Cost Basis	1,118	1,118
Total	31,239	31,467
Special Mention \| Real Estate: \| Residential
Total Loans
2026/2025	0	785
2025/2024	356	0
2024/2023	0	0
2023/2022	0	1,541
2022/2021	1,529	0
Prior	1	0
Revolving Loans Amortized Cost Basis	0	0
Total	1,886	2,326
Special Mention \| Real Estate: \| Commercial
Total Loans
2026/2025	0	824
2025/2024	621	5,513
2024/2023	5,493	519
2023/2022	0	0
2022/2021	0	7,466
Prior	12,493	1,169
Revolving Loans Amortized Cost Basis	0	0
Total	18,607	15,491
Special Mention \| Real Estate: \| Construction
Total Loans
2026/2025	0	0
2025/2024	0	0
2024/2023	0	0
2023/2022	0	0
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	0	0
Special Mention \| Commercial and Industrial
Total Loans
2026/2025	0	1,780
2025/2024	0	139
2024/2023	0	0
2023/2022	0	0
2022/2021	0	0
Prior	110	163
Revolving Loans Amortized Cost Basis	0	300
Total	110	2,382
Special Mention \| Consumer
Total Loans
2026/2025	0	0
2025/2024	0	0
2024/2023	0	0
2023/2022	0	0
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	0	0
Special Mention \| Other
Total Loans
2026/2025	0	0
2025/2024	0	0
2024/2023	0	0
2023/2022	0	0
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	0	0
Substandard \| Real Estate: \| Residential
Total Loans
2026/2025	0	0
2025/2024	427	0
2024/2023	0	2,139
2023/2022	2,113	0
2022/2021	73	0
Prior	616	592
Revolving Loans Amortized Cost Basis	0	0
Total	3,229	2,731
Substandard \| Real Estate: \| Commercial
Total Loans
2026/2025	0	0
2025/2024	200	1,962
2024/2023	0	0
2023/2022	0	0
2022/2021	0	0
Prior	225	95
Revolving Loans Amortized Cost Basis	0	0
Total	425	2,057
Substandard \| Real Estate: \| Construction
Total Loans
2026/2025	0	0
2025/2024	0	0
2024/2023	0	754
2023/2022	812	0
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	812	754
Substandard \| Commercial and Industrial
Total Loans
2026/2025	0	0
2025/2024	1,704	0
2024/2023	131	0
2023/2022	0	0
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	1,835	0
Substandard \| Consumer
Total Loans
2026/2025	0	0
2025/2024	0	0
2024/2023	0	0
2023/2022	0	0
2022/2021	0	25
Prior	89	82
Revolving Loans Amortized Cost Basis	0	0
Total	89	107
Substandard \| Other
Total Loans
2026/2025	0	0
2025/2024	0	0
2024/2023	0	0
2023/2022	0	0
2022/2021	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Total	$ 0	$ 0

Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process, Write Off

No definition available.

Name:	cbfv_FinancingReceivableBeforeAllowanceForCreditLossFeeAndLoanInProcessWriteOff
Namespace Prefix:	cbfv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year, Write Off

+ References

No definition available.

+ Details

Name:	cbfv_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossByOriginationYearWriteOffAbstract
Namespace Prefix:	cbfv_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost, before allowance for credit loss, fee, and loan in process, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

+ Details

Name:	us-gaap_FinancingReceivableBeforeAllowanceForCreditLossAndFee
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossByOriginationYearAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-79

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of writeoff of financing receivable originated more than five years before current fiscal year. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, of financing receivable that can be withdrawn, repaid, and redrawn.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestRevolving
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of writeoff of financing receivable that can be withdrawn, repaid, and redrawn.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of writeoff of financing receivable originated four years before current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of writeoff of financing receivable originated three years before current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, of financing receivable originated in current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of writeoff of financing receivable originated in current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of writeoff of financing receivable originated two years before current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amortized cost excluding accrued interest of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, excluding accrued interest, of writeoff of financing receivable originated in fiscal year before current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=cbfv_RealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=cbfv_CommercialAndIndustrialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=cbfv_OtherPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_PassMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SpecialMentionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SubstandardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: