Premises and Equipment: Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 42,650	$ 41,590
Less accumulated depreciation	21,164	19,948
Premises and equipment, net	21,486	21,642
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	5,404	5,404
Buildings and improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	25,592	25,178
Furniture and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	11,316	10,715
Property held for future expansion
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	116	116
Construction and purchases in progress
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 222	$ 177