XML 106 R66.htm IDEA: XBRL DOCUMENT
v3.20.1

Loans and ALLL (Narrative) (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 USD ($) loan NumberofLoan | Dec. 31, 2018 USD ($) loan NumberofLoan
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | loan | 0 | 0
Restructure of Loans through Forbearance of Principal or Accrued Interest | NumberofLoan | 0 | 0
Migration analysis of loan portfolio period | 5 years |
Threshold period of continuous performance to return loans to accrual status | 6 months |
Advance in connection with impaired loans | $ 175 | $ 542
Minimum [Member] | 4 - Low satisfactory [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Delinquency period | 10 days |
Minimum [Member] | 5 - Special mention [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Delinquency period | 30 days |
Maximum [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing receivable, amortization term | 30 years |
Maximum [Member] | 4 - Low satisfactory [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Delinquency period | 30 days |
Maximum [Member] | 5 - Special mention [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Delinquency period | 60 days |
Commercial, Agricultural, and Residential Portfolio Segments [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Number of days past due (or more), accrual of interest discontinued | 90 days |
Consumer [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Maximum days of consumer loan charged off | 180 days |
Consumer [Member] | Maximum [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing receivable, amortization term | 15 years |
Commercial and Agricultural [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Maximum percentage of loan | 0.80 |
Commercial and Agricultural [Member] | Customer Concentration Risk [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Maximum amount of loans | $ 15,000 |
Residential Real Estate [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Maximum percentage of loan | 1 |
Maximum percentage of principal, interest, taxes and hazard insurance on property over gross income | 0.28 |
Maximum percentage of debt servicing over gross income | 0.40 |
Maximum amount without corporation approval | $ 1,000 |
Residential, Privately Insured, Financing Receivable [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Maximum percentage of loan | 0.80 |

X
- Definition Financing Receivable, Allowance For Credit Losses, Historical Loss Allocation Analysis Period + References No definition available. + Details
Name: | isba_FinancingReceivableAllowanceForCreditLossesHistoricalLossAllocationAnalysisPeriod
Namespace Prefix: | isba_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financing Receivable, Amount, Additional Approval Threshold + References No definition available. + Details
Name: | isba_FinancingReceivableAmountAdditionalApprovalThreshold
Namespace Prefix: | isba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Financing Receivable, Continuing Performance, Accrual Of Interest, Threshold Period + References No definition available. + Details
Name: | isba_FinancingReceivableContinuingPerformanceAccrualOfInterestThresholdPeriod
Namespace Prefix: | isba_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financing Receivable, Credit Quality, Delinquency Period + References No definition available. + Details
Name: | isba_FinancingReceivableCreditQualityDelinquencyPeriod
Namespace Prefix: | isba_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financing Receivable, Debt Servicing To Gross Income Ratio, Maximum + References No definition available. + Details
Name: | isba_FinancingReceivableDebtServicingToGrossIncomeRatioMaximum
Namespace Prefix: | isba_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financing Receivable, Loan To Value Ratio, Maximum + References No definition available. + Details
Name: | isba_FinancingReceivableLoanToValueRatioMaximum
Namespace Prefix: | isba_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financing Receivable, Nonperforming, Nonaccrual Of Interest, Threshold Period + References No definition available. + Details
Name: | isba_FinancingReceivableNonperformingNonaccrualOfInterestThresholdPeriod
Namespace Prefix: | isba_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financing Receivable, Payment Amount To Gross Income Ratio, Maximum + References No definition available. + Details
Name: | isba_FinancingReceivablePaymentAmountToGrossIncomeRatioMaximum
Namespace Prefix: | isba_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financing Receivable, Term + References No definition available. + Details
Name: | isba_FinancingReceivableTerm
Namespace Prefix: | isba_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Restructure of loans through the forbearance of principal or accrued interest. + References No definition available. + Details
Name: | isba_RestructureOfLoansThroughForbearanceOfPrincipalOrAccruedInterest
Namespace Prefix: | isba_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- 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_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13537-108611 + Details
Name: | us-gaap_ConcentrationRiskCreditRiskFinancialInstrumentMaximumExposure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reflects the unfunded portion of contractual agreements to lend funds to borrowers for loans whose terms have been modified by troubled debt restructuring. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 40 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18794-111554 + Details
Name: | us-gaap_LoansAndLeasesReceivableImpairedCommitmentToLend
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Threshold period past due for financing receivable to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_ThresholdPeriodPastDueForWriteoffOfFinancingReceivable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=isba_LowSatisfactoryRatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=isba_CommercialAgriculturalandResidentialPortfolioSegmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=isba_CommercialAndAgriculturalPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=isba_ResidentialPrivatelyInsuredFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |