Fair Value (Estimated Fair Value Of Financial Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Carrying Amount
Assets
Investment securities available-for-sale	$ 520,659	$ 526,251
Mortgage loans held for sale	57,662	17,775
Loans, net:
Federal Home Loan Bank stock	235,363	228,494
Cash collateral held by counterparty	6,910	7,844
Liabilities:
Borrowed funds	4,870,219	4,792,847
Carrying Amount | Checking and passbook accounts
Liabilities:
Deposit accounts	1,957,745	2,150,770
Carrying Amount | Certificates of Deposit
Liabilities:
Deposit accounts	8,489,223	8,044,309
Carrying Amount | Borrowers' Advances for Taxes and Insurance
Liabilities:
Other liabilities	113,168	113,637
Carrying Amount | Principal, Interest, And Related Escrow Owed On Loans Serviced
Liabilities:
Other liabilities	30,328	28,753
Carrying Amount | Forward Commitments For Sale Of Mortgage Loans
Liabilities:
Derivative liability	351	72
Carrying Amount | Cash and due from banks
Assets
Cash and Cash Equivalents	24,176	26,287
Carrying Amount | Interest Earning Cash Equivalents
Assets
Cash and Cash Equivalents	405,263	437,431
Carrying Amount | Mortgage Receivable
Loans, net:
Loans, net	15,655,159	15,316,354
Carrying Amount | Other Loans
Loans, net:
Loans, net	8,153	5,705
Carrying Amount | Accrued Interest Receivable
Loans, net:
Accrued interest receivable	62,553	59,398
Carrying Amount | Interest Rate Lock Commitments
Loans, net:
Derivative Asset, Fair Value	272	395
Investment securities available-for-sale	520,659	526,251
Mortgage loans held for sale	58,325	17,986
Federal Home Loan Bank stock	235,363	228,494
Cash collateral held by counterparty	6,910	7,844
Liabilities:
Borrowed funds	4,892,273	4,819,873
Fair Value, Measurements, Recurring
Assets
Mortgage loans held for sale	22,861	10,713
Checking and passbook accounts
Liabilities:
Deposit accounts	1,957,745	2,150,770
Certificates of Deposit
Liabilities:
Deposit accounts	8,511,443	7,989,992
Borrowers' Advances for Taxes and Insurance
Liabilities:
Other liabilities	113,168	113,637
Principal, Interest, And Related Escrow Owed On Loans Serviced
Liabilities:
Other liabilities	30,328	28,753
Forward Commitments For Sale Of Mortgage Loans
Liabilities:
Derivative liability	351	72
Forward Commitments For Sale Of Mortgage Loans | Fair Value, Measurements, Recurring
Liabilities:
Derivative liability	351	72
Cash and due from banks
Assets
Cash and Cash Equivalents	24,176	26,287
Interest Earning Cash Equivalents
Assets
Cash and Cash Equivalents	405,263	437,431
Mortgage Receivable
Loans, net:
Loans, net	14,564,394	13,922,944
Other Loans
Loans, net:
Loans, net	8,153	5,705
Accrued Interest Receivable
Loans, net:
Accrued interest receivable	62,553	59,398
Interest Rate Lock Commitments
Loans, net:
Derivative Asset, Fair Value	272	395
Interest Rate Lock Commitments | Fair Value, Measurements, Recurring
Loans, net:
Derivative Asset, Fair Value	272	395
Fair Value, Inputs, Level 1
Assets
Investment securities available-for-sale	0	0
Mortgage loans held for sale	0	0
Loans, net:
Cash collateral held by counterparty	6,910	7,844
Liabilities:
Borrowed funds	0	0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Assets
Mortgage loans held for sale	0	0
Fair Value, Inputs, Level 1 | Checking and passbook accounts
Liabilities:
Deposit accounts	0	0
Fair Value, Inputs, Level 1 | Certificates of Deposit
Liabilities:
Deposit accounts	0	0
Fair Value, Inputs, Level 1 | Borrowers' Advances for Taxes and Insurance
Liabilities:
Other liabilities	0	0
Fair Value, Inputs, Level 1 | Principal, Interest, And Related Escrow Owed On Loans Serviced
Liabilities:
Other liabilities	0	0
Fair Value, Inputs, Level 1 | Forward Commitments For Sale Of Mortgage Loans
Liabilities:
Derivative liability	0	0
Fair Value, Inputs, Level 1 | Forward Commitments For Sale Of Mortgage Loans | Fair Value, Measurements, Recurring
Liabilities:
Derivative liability	0	0
Fair Value, Inputs, Level 1 | Cash and due from banks
Assets
Cash and Cash Equivalents	24,176	26,287
Fair Value, Inputs, Level 1 | Interest Earning Cash Equivalents
Assets
Cash and Cash Equivalents	405,263	437,431
Fair Value, Inputs, Level 1 | Mortgage Receivable
Loans, net:
Loans, net	0	0
Fair Value, Inputs, Level 1 | Other Loans
Loans, net:
Loans, net	0	0
Fair Value, Inputs, Level 1 | Accrued Interest Receivable
Loans, net:
Accrued interest receivable	0	0
Fair Value, Inputs, Level 1 | Interest Rate Lock Commitments
Loans, net:
Derivative Asset, Fair Value	0	0
Fair Value, Inputs, Level 1 | Interest Rate Lock Commitments | Fair Value, Measurements, Recurring
Loans, net:
Derivative Asset, Fair Value	0	0
Fair Value, Inputs, Level 2
Assets
Investment securities available-for-sale	520,659	526,251
Mortgage loans held for sale	58,325	17,986
Loans, net:
Federal Home Loan Bank stock	0	0
Cash collateral held by counterparty	0	0
Liabilities:
Borrowed funds	4,892,273	4,819,873
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Assets
Mortgage loans held for sale	22,861	10,713
Fair Value, Inputs, Level 2 | Checking and passbook accounts
Liabilities:
Deposit accounts	1,957,745	2,150,770
Fair Value, Inputs, Level 2 | Certificates of Deposit
Liabilities:
Deposit accounts	8,511,443	7,989,992
Fair Value, Inputs, Level 2 | Borrowers' Advances for Taxes and Insurance
Liabilities:
Other liabilities	113,168	113,637
Fair Value, Inputs, Level 2 | Principal, Interest, And Related Escrow Owed On Loans Serviced
Liabilities:
Other liabilities	30,328	28,753
Fair Value, Inputs, Level 2 | Forward Commitments For Sale Of Mortgage Loans
Liabilities:
Derivative liability	351	72
Fair Value, Inputs, Level 2 | Forward Commitments For Sale Of Mortgage Loans | Fair Value, Measurements, Recurring
Liabilities:
Derivative liability	351	72
Fair Value, Inputs, Level 2 | Cash and due from banks
Assets
Cash and Cash Equivalents	0	0
Fair Value, Inputs, Level 2 | Interest Earning Cash Equivalents
Assets
Cash and Cash Equivalents	0	0
Fair Value, Inputs, Level 2 | Mortgage Receivable
Loans, net:
Loans, net	0	0
Fair Value, Inputs, Level 2 | Other Loans
Loans, net:
Loans, net	0	0
Fair Value, Inputs, Level 2 | Accrued Interest Receivable
Loans, net:
Accrued interest receivable	62,553	59,398
Fair Value, Inputs, Level 2 | Interest Rate Lock Commitments
Loans, net:
Derivative Asset, Fair Value	0	0
Fair Value, Inputs, Level 2 | Interest Rate Lock Commitments | Fair Value, Measurements, Recurring
Loans, net:
Derivative Asset, Fair Value	0	0
Fair Value, Inputs, Level 3
Assets
Investment securities available-for-sale	0	0
Mortgage loans held for sale	0	0
Loans, net:
Federal Home Loan Bank stock	0	0
Cash collateral held by counterparty	0	0
Liabilities:
Borrowed funds	0	0
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Assets
Mortgage loans held for sale	0	0
Fair Value, Inputs, Level 3 | Checking and passbook accounts
Liabilities:
Deposit accounts	0	0
Fair Value, Inputs, Level 3 | Certificates of Deposit
Liabilities:
Deposit accounts	0	0
Fair Value, Inputs, Level 3 | Borrowers' Advances for Taxes and Insurance
Liabilities:
Other liabilities	0	0
Fair Value, Inputs, Level 3 | Principal, Interest, And Related Escrow Owed On Loans Serviced
Liabilities:
Other liabilities	0	0
Fair Value, Inputs, Level 3 | Forward Commitments For Sale Of Mortgage Loans
Liabilities:
Derivative liability	0	0
Fair Value, Inputs, Level 3 | Forward Commitments For Sale Of Mortgage Loans | Fair Value, Measurements, Recurring
Liabilities:
Derivative liability	0	0
Fair Value, Inputs, Level 3 | Cash and due from banks
Assets
Cash and Cash Equivalents	0	0
Fair Value, Inputs, Level 3 | Interest Earning Cash Equivalents
Assets
Cash and Cash Equivalents	0	0
Fair Value, Inputs, Level 3 | Mortgage Receivable
Loans, net:
Loans, net	14,564,394	13,922,944
Fair Value, Inputs, Level 3 | Other Loans
Loans, net:
Loans, net	8,153	5,705
Fair Value, Inputs, Level 3 | Accrued Interest Receivable
Loans, net:
Accrued interest receivable	0	0
Fair Value, Inputs, Level 3 | Interest Rate Lock Commitments
Loans, net:
Derivative Asset, Fair Value	272	395
Fair Value, Inputs, Level 3 | Interest Rate Lock Commitments | Fair Value, Measurements, Recurring
Loans, net:
Derivative Asset, Fair Value	$ 272	$ 395