XML 57 R47.htm IDEA: XBRL DOCUMENT
v3.21.2

Loans and ALLL (Summary of information pertaining to impaired loans) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020
Impaired Financing Receivable, Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Outstanding Balance | $ 6,732 |  | $ 6,732 |  | $ 9,823
Impaired loans without a valuation allowance, Outstanding Balance | 22,936 |  | 22,936 |  | 18,113
Impaired loans, Outstanding Balance | 29,668 |  | 29,668 |  | 27,936
Impaired Financing Receivable, Unpaid Principal Balance [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Unpaid Principal Balance | 7,004 |  | 7,004 |  | 10,407
Impaired loans without a valuation allowance, Unpaid Principal Balance | 23,252 |  | 23,252 |  | 18,237
Impaired loans, Unpaid Principal Balance | 30,256 |  | 30,256 |  | 28,644
Impaired loans, Valuation Allowance | 583 |  | 583 |  | 911
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Average Outstanding Balance | 8,146 | $ 10,159 | 8,601 | $ 10,064 |
Impaired loans without a valuation allowance, Average Outstanding Balance | 21,957 | 17,339 | 22,478 | 17,405 |
Impaired loans, Average Outstanding Balance | 30,103 | 27,498 | 31,079 | 27,469 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Interest Income Recognized | 75 | 143 | 263 | 391 |
Impaired loans without a valuation allowance, Interest Income Recognized | 301 | 191 | 926 | 571 |
Impaired loans, Interest Income Recognized | 376 | 334 | 1,189 | 962 |
Total commercial [Member] |  |  |  |  |
Impaired Financing Receivable, Recorded Investment [Abstract] |  |  |  |  |
Impaired loans, Outstanding Balance | 11,563 |  | 11,563 |  | 9,821
Impaired Financing Receivable, Unpaid Principal Balance [Abstract] |  |  |  |  |
Impaired loans, Unpaid Principal Balance | 11,879 |  | 11,879 |  | 10,137
Impaired loans, Valuation Allowance | 21 |  | 21 |  | 84
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans, Average Outstanding Balance | 11,785 | 9,794 | 12,333 | 8,815 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans, Interest Income Recognized | 168 | 152 | 511 | 370 |
Commercial real estate [Member] |  |  |  |  |
Impaired Financing Receivable, Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Outstanding Balance | 197 |  | 197 |  | 2,048
Impaired loans without a valuation allowance, Outstanding Balance | 8,021 |  | 8,021 |  | 3,006
Impaired Financing Receivable, Unpaid Principal Balance [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Unpaid Principal Balance | 197 |  | 197 |  | 2,290
Impaired loans without a valuation allowance, Unpaid Principal Balance | 8,337 |  | 8,337 |  | 3,080
Impaired loans, Valuation Allowance | 13 |  | 13 |  | 79
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Average Outstanding Balance | 1,377 | 1,564 | 2,161 | 1,157 |
Impaired loans without a valuation allowance, Average Outstanding Balance | 7,013 | 3,285 | 6,109 | 3,964 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Interest Income Recognized | 3 | 37 | 66 | 83 |
Impaired loans without a valuation allowance, Interest Income Recognized | 121 | 43 | 315 | 162 |
Commercial other [Member] |  |  |  |  |
Impaired Financing Receivable, Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Outstanding Balance | 3,053 |  | 3,053 |  | 107
Impaired loans without a valuation allowance, Outstanding Balance | 292 |  | 292 |  | 4,660
Impaired Financing Receivable, Unpaid Principal Balance [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Unpaid Principal Balance | 3,053 |  | 3,053 |  | 107
Impaired loans without a valuation allowance, Unpaid Principal Balance | 292 |  | 292 |  | 4,660
Impaired loans, Valuation Allowance | 8 |  | 8 |  | 5
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Average Outstanding Balance | 3,090 | 442 | 1,569 | 454 |
Impaired loans without a valuation allowance, Average Outstanding Balance | 305 | 4,503 | 2,494 | 3,240 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Interest Income Recognized | 35 | 13 | 71 | 19 |
Impaired loans without a valuation allowance, Interest Income Recognized | 9 | 59 | 59 | 106 |
Total agricultural [Member] |  |  |  |  |
Impaired Financing Receivable, Recorded Investment [Abstract] |  |  |  |  |
Impaired loans, Outstanding Balance | 14,623 |  | 14,623 |  | 13,796
Impaired Financing Receivable, Unpaid Principal Balance [Abstract] |  |  |  |  |
Impaired loans, Unpaid Principal Balance | 14,623 |  | 14,623 |  | 13,846
Impaired loans, Valuation Allowance | 0 |  | 0 |  | 56
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans, Average Outstanding Balance | 14,733 | 13,048 | 14,838 | 13,574 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans, Interest Income Recognized | 171 | 134 | 563 | 435 |
Agricultural real estate [Member] |  |  |  |  |
Impaired Financing Receivable, Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Outstanding Balance | 0 |  | 0 |  | 1,994
Impaired loans without a valuation allowance, Outstanding Balance | 9,814 |  | 9,814 |  | 8,681
Impaired Financing Receivable, Unpaid Principal Balance [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Unpaid Principal Balance | 0 |  | 0 |  | 1,994
Impaired loans without a valuation allowance, Unpaid Principal Balance | 9,814 |  | 9,814 |  | 8,731
Impaired loans, Valuation Allowance | 0 |  | 0 |  | 54
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Average Outstanding Balance | 94 | 2,198 | 737 | 2,100 |
Impaired loans without a valuation allowance, Average Outstanding Balance | 9,845 | 7,548 | 9,760 | 7,590 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Interest Income Recognized | 0 | 27 | 11 | 77 |
Impaired loans without a valuation allowance, Interest Income Recognized | 113 | 68 | 378 | 214 |
Agricultural other [Member] |  |  |  |  |
Impaired Financing Receivable, Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Outstanding Balance | 0 |  | 0 |  | 1,355
Impaired loans without a valuation allowance, Outstanding Balance | 4,809 |  | 4,809 |  | 1,766
Impaired Financing Receivable, Unpaid Principal Balance [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Unpaid Principal Balance | 0 |  | 0 |  | 1,355
Impaired loans without a valuation allowance, Unpaid Principal Balance | 4,809 |  | 4,809 |  | 1,766
Impaired loans, Valuation Allowance | 0 |  | 0 |  | 2
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Average Outstanding Balance | 0 | 1,355 | 226 | 1,355 |
Impaired loans without a valuation allowance, Average Outstanding Balance | 4,794 | 1,947 | 4,115 | 2,529 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Interest Income Recognized | 0 | 18 | 0 | 60 |
Impaired loans without a valuation allowance, Interest Income Recognized | 58 | 21 | 174 | 84 |
Total residential real estate [Member] |  |  |  |  |
Impaired Financing Receivable, Recorded Investment [Abstract] |  |  |  |  |
Impaired loans, Outstanding Balance | 3,482 |  | 3,482 |  | 4,319
Impaired Financing Receivable, Unpaid Principal Balance [Abstract] |  |  |  |  |
Impaired loans, Unpaid Principal Balance | 3,754 |  | 3,754 |  | 4,661
Impaired loans, Valuation Allowance | 562 |  | 562 |  | 771
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans, Average Outstanding Balance | 3,585 | 4,656 | 3,908 | 5,079 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans, Interest Income Recognized | 37 | 48 | 115 | 157 |
Residential real estate senior liens [Member] |  |  |  |  |
Impaired Financing Receivable, Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Outstanding Balance | 3,482 |  | 3,482 |  | 4,319
Impaired Financing Receivable, Unpaid Principal Balance [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Unpaid Principal Balance | 3,754 |  | 3,754 |  | 4,661
Impaired loans, Valuation Allowance | 562 |  | 562 |  | $ 771
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Average Outstanding Balance | 3,585 | 4,600 | 3,908 | 4,998 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans with a valuation allowance, Interest Income Recognized | 37 | 48 | 115 | 152 |
Residential real estate home equity lines of credit [Member] |  |  |  |  |
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans without a valuation allowance, Average Outstanding Balance | 0 | 56 | 0 | 81 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans without a valuation allowance, Interest Income Recognized | 0 | 0 | 0 | 5 |
Total Consumer [Member] |  |  |  |  |
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans, Average Outstanding Balance | 0 | 0 | 0 | 1 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans, Interest Income Recognized | $ 0 | $ 0 | 0 | 0 |
Consumer secured [Member] |  |  |  |  |
Impaired Financing Receivable, Average Recorded Investment [Abstract] |  |  |  |  |
Impaired loans without a valuation allowance, Average Outstanding Balance |  |  | 0 | 1 |
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract] |  |  |  |  |
Impaired loans without a valuation allowance, Interest Income Recognized |  |  | $ 0 | $ 0 |

X
- Definition Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5258-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_ImpairedFinancingReceivableAverageRecordedInvestmentAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethodAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953550-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_ImpairedFinancingReceivableRecordedInvestmentAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of allowance for credit losses related to recorded investment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableRelatedAllowance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalanceAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5258-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of investment in impaired financing receivables for which there is no related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953550-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5258-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of investment in impaired financing receivables for which there is a related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953550-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=isba_CommercialOtherPortfolioSegmentMember
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_AgriculturalRealEstatePortfolioSegmentMember
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_ResidentialHomeEquityLineOfCreditFinancingReceivableMember
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_ConsumerSecuredFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |