Loan Portfolio and Allowance for Credit Losses - Performance of Loans Modified to Borrowers Experiencing Financial Difficulty (Details) - USD ($) $ in Thousands		Sep. 30, 2025	Sep. 30, 2024
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		$ 862	$ 685
Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
New York and other states [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	532	512
New York and other states [Member] | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
FLORIDA
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		330	173
FLORIDA | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
Commercial Real Estate [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
Commercial Real Estate [Member] | New York and other states [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
Commercial Real Estate [Member] | FLORIDA | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
Other [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
Other [Member] | New York and other states [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
Other [Member] | FLORIDA | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
First Mortgages [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		675	354
First Mortgages [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	392	270
First Mortgages [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		283	84
Home Equity Loans [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		18	89
Home Equity Loans [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	18	0
Home Equity Loans [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	89
Home Equity Line of Credit [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		169	242
Home Equity Line of Credit [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	122	242
Home Equity Line of Credit [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		47	0
Current [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		502	685
Current [Member] | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
Current [Member] | New York and other states [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	172	512
Current [Member] | New York and other states [Member] | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
Current [Member] | FLORIDA
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		330	173
Current [Member] | FLORIDA | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
Current [Member] | Commercial Real Estate [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
Current [Member] | Commercial Real Estate [Member] | New York and other states [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
Current [Member] | Commercial Real Estate [Member] | FLORIDA | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
Current [Member] | Other [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
Current [Member] | Other [Member] | New York and other states [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
Current [Member] | Other [Member] | FLORIDA | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
Current [Member] | First Mortgages [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		437	354
Current [Member] | First Mortgages [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	154	270
Current [Member] | First Mortgages [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		283	84
Current [Member] | Home Equity Loans [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		18	89
Current [Member] | Home Equity Loans [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	18	0
Current [Member] | Home Equity Loans [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	89
Current [Member] | Home Equity Line of Credit [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		47	242
Current [Member] | Home Equity Line of Credit [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	242
Current [Member] | Home Equity Line of Credit [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		47	0
30 - 59 Days Past Due [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		122	0
30 - 59 Days Past Due [Member] | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | New York and other states [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	122	0
30 - 59 Days Past Due [Member] | New York and other states [Member] | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
30 - 59 Days Past Due [Member] | FLORIDA
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | FLORIDA | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | Commercial Real Estate [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | Commercial Real Estate [Member] | New York and other states [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
30 - 59 Days Past Due [Member] | Commercial Real Estate [Member] | FLORIDA | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | Other [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | Other [Member] | New York and other states [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
30 - 59 Days Past Due [Member] | Other [Member] | FLORIDA | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | First Mortgages [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | First Mortgages [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
30 - 59 Days Past Due [Member] | First Mortgages [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | Home Equity Loans [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | Home Equity Loans [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
30 - 59 Days Past Due [Member] | Home Equity Loans [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
30 - 59 Days Past Due [Member] | Home Equity Line of Credit [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		122	0
30 - 59 Days Past Due [Member] | Home Equity Line of Credit [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	122	0
30 - 59 Days Past Due [Member] | Home Equity Line of Credit [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		238	0
60 - 89 Days Past Due [Member] | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | New York and other states [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	238	0
60 - 89 Days Past Due [Member] | New York and other states [Member] | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
60 - 89 Days Past Due [Member] | FLORIDA
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | FLORIDA | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | Commercial Real Estate [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | Commercial Real Estate [Member] | New York and other states [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
60 - 89 Days Past Due [Member] | Commercial Real Estate [Member] | FLORIDA | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | Other [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | Other [Member] | New York and other states [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
60 - 89 Days Past Due [Member] | Other [Member] | FLORIDA | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | First Mortgages [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		238	0
60 - 89 Days Past Due [Member] | First Mortgages [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	238	0
60 - 89 Days Past Due [Member] | First Mortgages [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | Home Equity Loans [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | Home Equity Loans [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
60 - 89 Days Past Due [Member] | Home Equity Loans [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | Home Equity Line of Credit [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
60 - 89 Days Past Due [Member] | Home Equity Line of Credit [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
60 - 89 Days Past Due [Member] | Home Equity Line of Credit [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | New York and other states [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
90+ Days Past Due [Member] | New York and other states [Member] | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
90+ Days Past Due [Member] | FLORIDA
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | FLORIDA | Installment [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | Commercial Real Estate [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | Commercial Real Estate [Member] | New York and other states [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
90+ Days Past Due [Member] | Commercial Real Estate [Member] | FLORIDA | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | Other [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | Other [Member] | New York and other states [Member] | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
90+ Days Past Due [Member] | Other [Member] | FLORIDA | Commercial [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | First Mortgages [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | First Mortgages [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
90+ Days Past Due [Member] | First Mortgages [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | Home Equity Loans [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | Home Equity Loans [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
90+ Days Past Due [Member] | Home Equity Loans [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | Home Equity Line of Credit [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		0	0
90+ Days Past Due [Member] | Home Equity Line of Credit [Member] | New York and other states [Member] | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans	[1]	0	0
90+ Days Past Due [Member] | Home Equity Line of Credit [Member] | FLORIDA | Real Estate Mortgage - 1 to 4 Family [Member]
Loan Portfolio and Allowance for Credit Losses [Abstract]
Performance of modified loans		$ 0	$ 0

[1] Includes New York, New Jersey, Vermont and Massachusetts.