XML 75 R62.htm IDEA: XBRL DOCUMENT v3.19.1

Loans and ALLL (Summary of information pertaining to TDRs) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	45	28
Pre-Modification Recorded Investment	$ 8,379	$ 8,266
Post-Modification Recorded Investment	$ 8,356	$ 8,266
Commercial other [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	4	6
Pre-Modification Recorded Investment	$ 1,360	$ 1,702
Post-Modification Recorded Investment	$ 1,360	$ 1,702
Agricultural other [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	31	15
Pre-Modification Recorded Investment	$ 6,318	$ 6,092
Post-Modification Recorded Investment	$ 6,295	$ 6,092
Total residential real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	10	7
Pre-Modification Recorded Investment	$ 701	$ 472
Post-Modification Recorded Investment	$ 701	$ 472
Residential real estate senior liens [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	10	6
Pre-Modification Recorded Investment	$ 701	$ 464
Post-Modification Recorded Investment	$ 701	$ 464
Residential real estate junior liens [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	0	1
Pre-Modification Recorded Investment	$ 0	$ 8
Post-Modification Recorded Investment	$ 0	$ 8
Below Market Interest Rate and Extension of Amortization Period [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	23	16
Pre-Modification Recorded Investment	$ 5,377	$ 6,286
Below Market Interest Rate and Extension of Amortization Period [Member] | Commercial other [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	3	6
Pre-Modification Recorded Investment	$ 1,186	$ 1,702
Below Market Interest Rate and Extension of Amortization Period [Member] | Agricultural other [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	13	4
Pre-Modification Recorded Investment	$ 3,693	$ 4,120
Below Market Interest Rate and Extension of Amortization Period [Member] | Total residential real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	7	6
Pre-Modification Recorded Investment	$ 498	$ 464
Below Market Interest Rate and Extension of Amortization Period [Member] | Residential real estate senior liens [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	7	6
Pre-Modification Recorded Investment	$ 498	$ 464
Below Market Interest Rate and Extension of Amortization Period [Member] | Residential real estate junior liens [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	0	0
Pre-Modification Recorded Investment	$ 0	$ 0
Interest Rate Below Market Reduction [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	22	12
Pre-Modification Recorded Investment	$ 3,002	$ 1,980
Interest Rate Below Market Reduction [Member] | Commercial other [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	1	0
Pre-Modification Recorded Investment	$ 174	$ 0
Interest Rate Below Market Reduction [Member] | Agricultural other [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	18	11
Pre-Modification Recorded Investment	$ 2,625	$ 1,972
Interest Rate Below Market Reduction [Member] | Total residential real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	3	1
Pre-Modification Recorded Investment	$ 203	$ 8
Interest Rate Below Market Reduction [Member] | Residential real estate senior liens [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	3	0
Pre-Modification Recorded Investment	$ 203	$ 0
Interest Rate Below Market Reduction [Member] | Residential real estate junior liens [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	0	1
Pre-Modification Recorded Investment	$ 0	$ 8

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

X

- Definition

Number of 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 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Post-modification amount of investment in financing receivables 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 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

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

X

- Definition

Pre-modification amount of investment in financing receivables 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 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=isba_CommercialOtherPortfolioSegmentMember
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=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=isba_ResidentialSeniorLiensFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=isba_ResidentialJuniorLiensFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=isba_BelowMarketInterestRateAndExtensionOfAmortizationPeriodMember
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: