Loans and Allowance for Loan Losses, Impaired Receivables (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2019	Dec. 31, 2018
Impaired loans by loans class [Abstract]
Recorded Investment		$ 21,161	$ 22,288
Unpaid Principal Balance		21,853	23,309
Related Allowance		0	0
Average Recorded Investment		21,907	23,161
New York and Other States [Member]
Impaired loans by loans class [Abstract]
Recorded Investment	[1]	18,686	19,546
Unpaid Principal Balance	[1]	19,378	20,461
Related Allowance	[1]	0	0
Average Recorded Investment	[1]	19,194	20,237
Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		2,475	2,742
Unpaid Principal Balance		2,475	2,848
Related Allowance		0	0
Average Recorded Investment		2,713	2,924
Commercial [Member] | Commercial Real Estate [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		1,430	1,386
Unpaid Principal Balance		1,601	1,556
Related Allowance		0	0
Average Recorded Investment		1,365	1,560
Commercial [Member] | Commercial Real Estate [Member] | New York and Other States [Member]
Impaired loans by loans class [Abstract]
Recorded Investment	[1]	1,319	1,274
Unpaid Principal Balance	[1]	1,490	1,444
Related Allowance	[1]	0	0
Average Recorded Investment	[1]	1,281	1,503
Commercial [Member] | Commercial Real Estate [Member] | Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		111	112
Unpaid Principal Balance		111	112
Related Allowance		0	0
Average Recorded Investment		84	57
Commercial [Member] | Other [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		37	38
Unpaid Principal Balance		87	88
Related Allowance		0	0
Average Recorded Investment		132	123
Commercial [Member] | Other [Member] | New York and Other States [Member]
Impaired loans by loans class [Abstract]
Recorded Investment	[1]	37	38
Unpaid Principal Balance	[1]	87	88
Related Allowance	[1]	0	0
Average Recorded Investment	[1]	132	123
Commercial [Member] | Other [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		0	0
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		16,952	17,503
Unpaid Principal Balance		17,263	18,060
Related Allowance		0	0
Average Recorded Investment		17,235	18,032
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]	14,922	15,210
Unpaid Principal Balance	[1]	15,233	15,661
Related Allowance	[1]	0	0
Average Recorded Investment	[1]	14,944	15,577
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		2,030	2,293
Unpaid Principal Balance		2,030	2,399
Related Allowance		0	0
Average Recorded Investment		2,291	2,455
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		329	336
Unpaid Principal Balance		349	356
Related Allowance		0	0
Average Recorded Investment		337	348
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]	247	252
Unpaid Principal Balance	[1]	267	272
Related Allowance	[1]	0	0
Average Recorded Investment	[1]	252	262
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		82	84
Unpaid Principal Balance		82	84
Related Allowance		0	0
Average Recorded Investment		85	86
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		2,413	3,025
Unpaid Principal Balance		2,553	3,249
Related Allowance		0	0
Average Recorded Investment		2,838	3,098
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]	2,161	2,772
Unpaid Principal Balance	[1]	2,301	2,996
Related Allowance	[1]	0	0
Average Recorded Investment	[1]	2,585	2,772
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | Florida [Member]
Impaired loans by loans class [Abstract]
Recorded Investment		252	253
Unpaid Principal Balance		252	253
Related Allowance		0	0
Average Recorded Investment		$ 253	$ 326

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