Loans and Allowance for Loan Losses, Impaired Receivables (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2021		Dec. 31, 2020
Impaired loans by loans class [Abstract]
Recorded Investment		$ 20,345		$ 21,581
Unpaid Principal Balance		20,965		22,253
Related Allowance		0		0
Average Recorded Investment		20,728		20,814
New York and Other States [Member]
Impaired loans by loans class [Abstract]
Recorded Investment	[1]	17,247		18,331
Unpaid Principal Balance	[1]	17,867		19,003
Related Allowance	[1]	0		0
Average Recorded Investment	[1]	17,812		17,892
Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		3,098		3,250
Unpaid Principal Balance		3,098		3,250
Related Allowance		0		0
Average Recorded Investment		2,916		2,922
Commercial [Member] | Commercial Real Estate [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		619		917
Unpaid Principal Balance		712		1,041
Related Allowance		0		0
Average Recorded Investment		1,258		1,291
Commercial [Member] | Commercial Real Estate [Member] | New York and Other States [Member]
Impaired loans by loans class [Abstract]
Recorded Investment	[1]	523		819
Unpaid Principal Balance	[1]	616		943
Related Allowance	[1]	0		0
Average Recorded Investment	[1]	1,152		1,186
Commercial [Member] | Commercial Real Estate [Member] | Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		96		98
Unpaid Principal Balance		96	[1]	98
Related Allowance		0		0
Average Recorded Investment		106		105
Commercial [Member] | Other [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		80		111
Unpaid Principal Balance		80		111
Related Allowance		0		0
Average Recorded Investment		106		103
Commercial [Member] | Other [Member] | New York and Other States [Member]
Impaired loans by loans class [Abstract]
Recorded Investment	[1]	80		111
Unpaid Principal Balance	[1]	80		111
Related Allowance	[1]	0		0
Average Recorded Investment	[1]	106		103
Commercial [Member] | Other [Member] | Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		0		0
Unpaid Principal Balance		0	[1]	0
Related Allowance		0		0
Average Recorded Investment		0		0
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		17,183		17,932
Unpaid Principal Balance		17,570		18,319
Related Allowance		0		0
Average Recorded Investment		16,606		16,665
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | New York and Other States [Member]
Impaired loans by loans class [Abstract]
Recorded Investment	[1]	14,425		15,024
Unpaid Principal Balance	[1]	14,812		15,411
Related Allowance	[1]	0		0
Average Recorded Investment	[1]	14,059		14,110
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		2,758		2,908
Unpaid Principal Balance		2,758		2,908
Related Allowance		0		0
Average Recorded Investment		2,547		2,555
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		214		219
Unpaid Principal Balance		214		240
Related Allowance		0		0
Average Recorded Investment		252		251
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | New York and Other States [Member]
Impaired loans by loans class [Abstract]
Recorded Investment	[1]	214		219
Unpaid Principal Balance	[1]	214		240
Related Allowance	[1]	0		0
Average Recorded Investment	[1]	235		235
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		0		0
Unpaid Principal Balance		0		0
Related Allowance		0		0
Average Recorded Investment		17		16
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		2,249		2,402
Unpaid Principal Balance		2,389		2,542
Related Allowance		0		0
Average Recorded Investment		2,506		2,504
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | New York and Other States [Member]
Impaired loans by loans class [Abstract]
Recorded Investment	[1]	2,005		2,158
Unpaid Principal Balance	[1]	2,145		2,298
Related Allowance	[1]	0		0
Average Recorded Investment	[1]	2,260		2,258
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		244		244
Unpaid Principal Balance		244		244
Related Allowance		0		0
Average Recorded Investment		$ 246		$ 246

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