XML 40 R28.htm IDEA: XBRL DOCUMENT
v3.25.1

Loans and ACL (Summary of Loan Composition) (Details) - USD ($) $ in Thousands | Mar. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 1,367,724 | $ 1,423,571
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 100.00% | 100.00%
Commercial and Industrial, Secured, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 220,884 | $ 221,510
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 16.15% | 15.56%
Commercial and Industrial, Unsecured, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 28,336 | $ 23,384
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 2.07% | 1.64%
Commercial [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 249,220 | $ 244,894
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 18.22% | 17.20%
Commercial Real Estate, Owner Occupied, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 183,228 | $ 178,376
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 13.40% | 12.53%
Commercial Real Estate, Non-owner Occupied |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 206,976 | $ 208,118
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 15.13% | 14.62%
Commercial Real Estate, 1-4 Family Investor, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 93,845 | $ 92,497
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 6.86% | 6.50%
Commercial Real Estate, Multifamily, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 68,185 | $ 68,456
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 4.99% | 4.81%
Commercial Real Estate |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 552,234 | $ 547,447
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 40.38% | 38.46%
Commercial Advances to Mortgage Brokers Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 3,015 | $ 63,080
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 0.22% | 4.43%
Agricultural Mortgage, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 65,699 | $ 67,550
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 4.80% | 4.75%
Agricultural Other Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 28,660 | $ 32,144
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 2.10% | 2.26%
Agricultural [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 94,359 | $ 99,694
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 6.90% | 7.01%
Residential Real Estate, Senior Lien, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 337,542 | $ 332,743
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 24.68% | 23.37%
Residential Real Estate, Junior Lien, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 9,409 | $ 8,655
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 0.69% | 0.61%
Residential Real Estate, Home Equity Lines of Credit, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 40,397 | $ 39,474
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 2.95% | 2.77%
Residential Mortgage |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 387,348 | $ 380,872
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 28.32% | 26.75%
Consumer, Secured, Direct, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 33,220 | $ 35,050
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 2.42% | 2.46%
Consumer, Secured, Indirect, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 45,081 | $ 49,136
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 3.30% | 3.45%
Consumer, Unsecured, Portfolio Segment |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 3,247 | $ 3,398
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 0.24% | 0.24%
Consumer Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 81,548 | $ 87,584
Financing Receivable, before Allowance for Credit Loss, to Total, Percent | 5.96% | 6.15%

X
- Definition Percentage, before allowance for credit loss, of financing receivable to total financing receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph c -Publisher SEC + Details
Name: | srt_FinancingReceivableBeforeAllowanceForCreditLossToTotalPercent
Namespace Prefix: | srt_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

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 Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 310 -SubTopic 20 -Name Accounting Standards Codification -Section 40 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481628/310-20-40-7 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481990/310-10-45-2 + Details
Name: | us-gaap_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-5 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

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

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

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

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=isba_CommercialRealEstate14FamilyInvestorPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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

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

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

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

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

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

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

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

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

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

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=isba_ConsumerUnsecuredPortfolioSegmentMember
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: |