Document and Entity Information - shares	6 Months Ended
	Mar. 31, 2018	May 01, 2018
Document and Entity Information
Entity Registrant Name	TIMBERLAND BANCORP INC,
Entity Central Index Key	0001046050
Current Fiscal Year End Date	--09-30
Entity Filer Category	Smaller Reporting Company
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		7,392,827