Loans Receivable and Allowance for Loan Losses: Loan Segment Risk Narrative (Details)	12 Months Ended
	Sep. 30, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ratio of loans to appraisal or purchase price (as a percent)	90.00%
Mortgage loans, one-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ratio of loans to appraisal or purchase price (as a percent)	90.00%
Ratio of loans to appraised value, private mortgage insurance requirement, percentage limit	80.00%
Mortgage loans, commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ratio of loans to appraisal or purchase price (as a percent)	80.00%
Mortgage loans, land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ratio of loans to appraisal or purchase price (as a percent)	75.00%