XML 43 R33.htm IDEA: XBRL DOCUMENT v3.25.3

Loans and ACL - Summary of Loan Modifications by Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	$ 9,056	$ 8,202	$ 9,056	$ 8,202
Current
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	9,056	8,202	9,056	8,202
30-59 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
60-89 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
90 Days or More
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Amortized Cost Basis		181	19	181
Other-Than-Insignificant Payment Delay
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	914		914	4,054
Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	925		5,509	12
Other-Than-Insignificant Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	443		1,006	1,038
Secured
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	4,114	1,937	4,114	1,937
Secured | Current
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	4,114	1,937	4,114	1,937
Secured | 30-59 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Secured | 60-89 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Secured | 90 Days or More
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Secured | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Amortized Cost Basis			$ 19	$ 0
% of Total Class of Financial Receivable			0.01%	0.00%
Secured | Other-Than-Insignificant Payment Delay
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	$ 0		$ 0	$ 1,926
% of Total Class of Financial Receivable	0.00%		0.00%	0.88%
Secured | Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	$ 0		$ 3,087	$ 11
% of Total Class of Financial Receivable	0.00%		1.26%	0.01%
Secured | Other-Than-Insignificant Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	$ 443		$ 1,006	$ 0
% of Total Class of Financial Receivable	0.18%		0.41%	0.00%
Commercial mortgage owner occupied
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	$ 2,832	823	$ 2,832	$ 823
Commercial mortgage owner occupied | Current
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	2,832	823	2,832	823
Commercial mortgage owner occupied | 30-59 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Commercial mortgage owner occupied | 60-89 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Commercial mortgage owner occupied | 90 Days or More
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Commercial mortgage owner occupied | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Amortized Cost Basis			$ 0	$ 0
% of Total Class of Financial Receivable			0.00%	0.00%
Commercial mortgage owner occupied | Other-Than-Insignificant Payment Delay
Financing Receivable, Modified [Line Items]
Amortized Cost Basis			$ 0	$ 823
% of Total Class of Financial Receivable			0.00%	0.48%
Commercial mortgage owner occupied | Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis			$ 1,497	$ 0
% of Total Class of Financial Receivable			0.84%	0.00%
Commercial mortgage owner occupied | Other-Than-Insignificant Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis			$ 0	$ 0
% of Total Class of Financial Receivable			0.00%	0.00%
Agricultural mortgage
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	1,185	1,305	$ 1,185	$ 1,305
Agricultural mortgage | Current
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	1,185	1,305	1,185	1,305
Agricultural mortgage | 30-59 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Agricultural mortgage | 60-89 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Agricultural mortgage | 90 Days or More
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Agricultural mortgage | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Amortized Cost Basis			$ 0	$ 0
% of Total Class of Financial Receivable			0.00%	0.00%
Agricultural mortgage | Other-Than-Insignificant Payment Delay
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	$ 914		$ 914	$ 1,305
% of Total Class of Financial Receivable	1.35%		1.35%	1.95%
Agricultural mortgage | Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	$ 0		$ 0	$ 0
% of Total Class of Financial Receivable	0.00%		0.00%	0.00%
Agricultural mortgage | Other-Than-Insignificant Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	$ 0		$ 0	$ 0
% of Total Class of Financial Receivable	0.00%		0.00%	0.00%
Agricultural other
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	$ 925	1,219	$ 925	$ 1,219
Agricultural other | Current
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	925	1,219	925	1,219
Agricultural other | 30-59 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Agricultural other | 60-89 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Agricultural other | 90 Days or More
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months	0	0	0	0
Agricultural other | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Amortized Cost Basis		$ 181	$ 0	$ 181
% of Total Class of Financial Receivable		0.60%	0.00%	0.60%
Agricultural other | Other-Than-Insignificant Payment Delay
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	$ 0		$ 0	$ 0
% of Total Class of Financial Receivable	0.00%		0.00%	0.00%
Agricultural other | Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	$ 925		$ 925	$ 0
% of Total Class of Financial Receivable	3.08%		3.08%	0.00%
Agricultural other | Other-Than-Insignificant Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis	$ 0		$ 0	$ 1,038
% of Total Class of Financial Receivable	0.00%		0.00%	3.46%
Secured - indirect
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months		$ 1		$ 1
Secured - indirect | Current
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months		1		1
Secured - indirect | 30-59 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months		0		0
Secured - indirect | 60-89 Days
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months		0		0
Secured - indirect | 90 Days or More
Financing Receivable, Modified [Line Items]
Financing receivable modified after 12 months		$ 0		0
Secured - indirect | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Amortized Cost Basis				$ 0
% of Total Class of Financial Receivable				0.00%
Secured - indirect | Other-Than-Insignificant Payment Delay
Financing Receivable, Modified [Line Items]
Amortized Cost Basis				$ 0
% of Total Class of Financial Receivable				0.00%
Secured - indirect | Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis				$ 1
% of Total Class of Financial Receivable				0.00%
Secured - indirect | Other-Than-Insignificant Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Amortized Cost Basis				$ 0
% of Total Class of Financial Receivable				0.00%

X

- Definition

Amortized cost excluding accrued interest, of financing receivable 12 months after modification for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestModifiedPast12Months
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Percentage of financing receivable modified during period for debtor experiencing financial difficulty to total financing receivables.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

Name:	us-gaap_FinancingReceivableModificationToTotalFinancingReceivablesPercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-34

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

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

X

- Definition

Amortized cost of financing receivable modified during period for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481933/310-10-55-12A

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 33
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-33

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-42

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetNotPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables30To59DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables60To89DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_InterestRateBelowMarketReductionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_PaymentDeferralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_ExtendedMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=isba_ExtendedMaturityAndPaymentDeferralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=isba_CommercialAndIndustrialSecuredPortfolioSegmentMember
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_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_ConsumerSecuredIndirectPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: