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Stock-based Compensation - Summary of ESOP Shares (Parenthetical) (Detail) - $ / shares | Sep. 30, 2021 | Jun. 30, 2021
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Employee Stock Ownership Plan Esop [Member] |  |
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] |  |
ESOP, closing price per share | $ 22.69 | $ 22.80

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

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- Definition Price of a single share of a number of saleable stocks of a company. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | us-gaap_EmployeeStockOwnershipPlanESOPDisclosuresByPlanAxis=iroq_EmployeeStockOwnershipPlanEsopMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |