Premises and Equipment: Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 40,601	$ 40,783
Less accumulated depreciation	18,703	18,416
Premises and equipment, net	21,898	22,367
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	24,764	24,718
Furniture and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	10,152	10,307
Property held for future expansion
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	129	129
Construction and purchases in progress
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 152	$ 225