Loan Commitments and Other Related Activities (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) loan	Dec. 31, 2016 USD ($)
Commitments to make loans
Loan commitments and other related activities
Contractual amounts of financial instruments - variable rate	$ 1,493	$ 3,808
Commitments to make loans \| Maximum
Loan commitments and other related activities
Period for which loan commitments are made	60 days
Commitments to make loans \| Multi-family
Loan commitments and other related activities
Number of loan commitments \| loan	2
Period for which initial interest rate is applicable	5 years
Commitments to make loans \| Multi-family \| Minimum
Loan commitments and other related activities
Initial interest rate (as a percent)	4.12%
Commitments to make loans \| Multi-family \| Maximum
Loan commitments and other related activities
Initial interest rate (as a percent)	4.18%
Unused lines of credit
Loan commitments and other related activities
Contractual amounts of financial instruments - variable rate	$ 2,582	$ 774

Represents the period for which the entity makes commitments to make loans.

No definition available.

Name:	byfc_CommitmentsToMakeLoansPeriods
Namespace Prefix:	byfc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the initial period for which the specified interest rate is applicable under commitments to make loans.

+ References

No definition available.

+ Details

Name:	byfc_LoanCommitmentsInitialInterestRatePeriod
Namespace Prefix:	byfc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of loan commitments as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	byfc_LoanCommitmentsNumber
Namespace Prefix:	byfc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the initial interest rate related to a commitment to make a loan.

+ References

No definition available.

+ Details

Name:	byfc_LoansInterestRateStatedPercentage
Namespace Prefix:	byfc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the amount of cash required to fully fund agreements to provide advances to borrowers and lessees at interest rates that increase or decrease depending on certain facts or circumstances.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 825
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=75032840&loc=d3e61082-112788

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 825
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=75032840&loc=d3e61044-112788

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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