XML 61 R51.htm IDEA: XBRL DOCUMENT v3.25.3

Fair Value - Recorded Amount of Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
AFS Securities
Total AFS securities	$ 511,970	$ 489,029
Total	518,578	492,012
Level 1
AFS Securities
Total	$ 0	$ 0
Percent of assets and liabilities measured at fair value	0.00%	0.00%
Level 2
AFS Securities
Total	$ 511,970	$ 489,029
Percent of assets and liabilities measured at fair value	98.73%	99.39%
Level 3
AFS Securities
Total	$ 6,608	$ 2,983
Percent of assets and liabilities measured at fair value	1.27%	0.61%
Recurring items
AFS Securities
Total AFS securities	$ 511,970	$ 489,029
Recurring items | U.S. Treasury
AFS Securities
Total AFS securities	206,041	220,571
Recurring items | States and political subdivisions
AFS Securities
Total AFS securities	71,102	76,568
Recurring items | Auction rate money market preferred
AFS Securities
Total AFS securities	2,790	3,044
Recurring items | Mortgage-backed securities
AFS Securities
Total AFS securities	23,397	26,886
Recurring items | Collateralized mortgage obligations
AFS Securities
Total AFS securities	201,213	154,674
Recurring items | Corporate
AFS Securities
Total AFS securities	7,427	7,286
Recurring items | Level 1
AFS Securities
Total AFS securities	0	0
Recurring items | Level 1 | U.S. Treasury
AFS Securities
Total AFS securities	0	0
Recurring items | Level 1 | States and political subdivisions
AFS Securities
Total AFS securities	0	0
Recurring items | Level 1 | Auction rate money market preferred
AFS Securities
Total AFS securities	0	0
Recurring items | Level 1 | Mortgage-backed securities
AFS Securities
Total AFS securities	0	0
Recurring items | Level 1 | Collateralized mortgage obligations
AFS Securities
Total AFS securities	0	0
Recurring items | Level 1 | Corporate
AFS Securities
Total AFS securities	0	0
Recurring items | Level 2
AFS Securities
Total AFS securities	511,970	489,029
Recurring items | Level 2 | U.S. Treasury
AFS Securities
Total AFS securities	206,041	220,571
Recurring items | Level 2 | States and political subdivisions
AFS Securities
Total AFS securities	71,102	76,568
Recurring items | Level 2 | Auction rate money market preferred
AFS Securities
Total AFS securities	2,790	3,044
Recurring items | Level 2 | Mortgage-backed securities
AFS Securities
Total AFS securities	23,397	26,886
Recurring items | Level 2 | Collateralized mortgage obligations
AFS Securities
Total AFS securities	201,213	154,674
Recurring items | Level 2 | Corporate
AFS Securities
Total AFS securities	7,427	7,286
Recurring items | Level 3
AFS Securities
Total AFS securities	0	0
Recurring items | Level 3 | U.S. Treasury
AFS Securities
Total AFS securities	0	0
Recurring items | Level 3 | States and political subdivisions
AFS Securities
Total AFS securities	0	0
Recurring items | Level 3 | Auction rate money market preferred
AFS Securities
Total AFS securities	0	0
Recurring items | Level 3 | Mortgage-backed securities
AFS Securities
Total AFS securities	0	0
Recurring items | Level 3 | Collateralized mortgage obligations
AFS Securities
Total AFS securities	0	0
Recurring items | Level 3 | Corporate
AFS Securities
Total AFS securities	0	0
Nonrecurring items
AFS Securities
Collateral dependent (net of ACL)	3,426	254
OMSR	2,164	2,185
Foreclosed assets	1,018	544
Nonrecurring items | Level 1
AFS Securities
Collateral dependent (net of ACL)	0	0
OMSR	0	0
Foreclosed assets	0	0
Nonrecurring items | Level 2
AFS Securities
Collateral dependent (net of ACL)	0	0
OMSR	0	0
Foreclosed assets	0	0
Nonrecurring items | Level 3
AFS Securities
Collateral dependent (net of ACL)	3,426	254
OMSR	2,164	2,185
Foreclosed assets	$ 1,018	$ 544

X

- Definition

Foreclosed Assets, Fair Value Disclosure

+ References

No definition available.

+ Details

Name:	isba_ForeclosedAssetsFairValueDisclosure
Namespace Prefix:	isba_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Impaired Financing Receivable, Fair Value Disclosure

+ References

No definition available.

+ Details

Name:	isba_ImpairedFinancingReceivableFairValueDisclosure
Namespace Prefix:	isba_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Other Mortgage Servicing Rights, Fair Value Disclosure

+ References

No definition available.

+ Details

Name:	isba_OtherMortgageServicingRightsFairValueDisclosure
Namespace Prefix:	isba_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Percent of assets and liabilities measured at fair value.

+ References

No definition available.

+ Details

Name:	isba_PercentageOfAssetsAndLiabilitiesMeasuredAtFairValue
Namespace Prefix:	isba_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Fair value portion of asset recognized for present right to economic benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

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

X

- References

No definition available.

+ Details

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

X

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-SubTopic 10
-Topic 825
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482881/825-10-55-10

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482736/825-10-45-1A

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-11

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-11

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-10

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482881/825-10-55-12

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 103
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-103

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 14: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481830/320-10-45-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

+ Details

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

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_AuctionRatePreferredSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_CollateralizedMortgageObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: