XML 54 R44.htm IDEA: XBRL DOCUMENT
v3.19.1

Loans Receivable - Narrative (Details) - USD ($) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2019 | Dec. 31, 2017 | Dec. 31, 2018
Receivables [Abstract] |  |  |
Reserve For Uncollected Loan Interest | $ 40,000 |  | $ 38,000
Financing receivable modifications | 17,000 |  |
Outstanding Commitments To Borrowers Loans Classified As Troubled Debt Restructurings | $ 0 | $ 0 |

X
- Definition Outstanding commitments to borrowers loans classified as troubled debt restructurings. + References No definition available. + Details
Name: | bfin_OutstandingCommitmentsToBorrowersLoansClassifiedAsTroubledDebtRestructurings
Namespace Prefix: | bfin_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Reserve for uncollected loan interest. + References No definition available. + Details
Name: | bfin_ReserveForUncollectedLoanInterest
Namespace Prefix: | bfin_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 40 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554 + Details
Name: | us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_ReceivablesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration