Document And Entity Information	9 Months Ended
	Jun. 30, 2017 shares
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Entity Registrant Name	First Savings Financial Group Inc
Entity Central Index Key	0001435508
Current Fiscal Year End Date	--09-30
Entity Filer Category	Smaller Reporting Company
Trading Symbol	FSFG
Entity Common Stock, Shares Outstanding	2,242,454