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v3.20.4

Note 13 - Loan Commitments and Other Off-balance-sheet Activities (Details) - USD ($) | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Commitments to Extend Credit [Member] |  |
Notional Or Contractual Credit Extension Commitments | $ 31,131 | $ 19,737
Standby Letters of Credit [Member] |  |
Notional Or Contractual Credit Extension Commitments | 6,668 | 6,119
Unused lines of Credit [Member] |  |
Notional Or Contractual Credit Extension Commitments | $ 200,240 | $ 149,771

X
- Definition Represents information related to national or contractual credit extension commitments. + References No definition available. + Details
Name: | bfin_NotionalOrContractualCreditExtensionCommitments
Namespace Prefix: | bfin_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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