The amount of reserve to cover probable credit losses related to financing receivables that were modified by troubled debt restructurings during the reporting period and were individually evaluated for impairment

No definition available.

+ Details

Name:	cbfv_AllowanceForLoanLossesOnTDRs
Namespace Prefix:	cbfv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=cbfv_AcquiredLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
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- Details

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

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Note 4 - Loans and Related Allowance for Loan Loss - Loans Classified as TDRs (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Number of contracts		0
Originated Loans [Member]
Number of contracts	1		1	1
Pre-modification outstanding recorded investment	$ 61,000		$ 61,000	$ 7,000
Nonperforming loans	61,000		61,000	7,000
Related allowance
Acquired Loans [Member]
Number of contracts				2
Pre-modification outstanding recorded investment				$ 576,000
Nonperforming loans			$ 1,953,000	584,000	$ 2,352,000
Related allowance
Residential Portfolio Segment [Member] \| Real Estate Sector [Member] \| Originated Loans [Member]
Number of contracts	1		1
Pre-modification outstanding recorded investment	$ 61,000		$ 61,000
Nonperforming loans	61,000		61,000
Related allowance
Residential Portfolio Segment [Member] \| Real Estate Sector [Member] \| Acquired Loans [Member]
Number of contracts				1
Pre-modification outstanding recorded investment				$ 37,000
Nonperforming loans			1,268	45,000	1,299
Related allowance
Other Portfolio Segment [Member] \| Originated Loans [Member]
Number of contracts				1
Pre-modification outstanding recorded investment				$ 7,000
Nonperforming loans			2,000	7,000	4,000
Related allowance
Commercial Portfolio Segment [Member] \| Real Estate Sector [Member] \| Originated Loans [Member]
Nonperforming loans			1,285,000		1,325,000
Commercial Portfolio Segment [Member] \| Real Estate Sector [Member] \| Acquired Loans [Member]
Number of contracts				1
Pre-modification outstanding recorded investment				$ 539,000
Nonperforming loans			$ 438,000	539,000	$ 660,000
Related allowance