DERIVATIVE FINANCIAL INSTRUMENTS - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
DERIVATIVE FINANCIAL INSTRUMENTS
Cash collateral derivative counterparty obligations	$ 1.5	$ 2.4

This information is pertaining to the cash collateral posted with certain derivative counterparties against its derivative obligations.

No definition available.

Name:	fsfg_CashCollateralDerivativeCounterpartyObligations
Namespace Prefix:	fsfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant