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Stock-based Compensation - Summary of ESOP Shares (Parenthetical) (Detail) - $ / shares	Dec. 31, 2019	Jun. 30, 2019
Employee Stock Ownership Plan Esop [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
ESOP, closing price per share	$ 23.02	$ 20.91

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

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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

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

X

- Details

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