Loan Portfolio and Allowance for Credit Losses, Risk Category of Loans (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Credit Risk Profile, Segregated by Class [Abstract]
Total loans		$ 4,799,582		$ 4,733,201
Current-period Gross writeoffs		48	$ 47
New York and Other States [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans	[1]	3,214,052		3,219,914	[2]
Current-period Gross writeoffs	[2]	17	46
Florida [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans		1,585,530		1,513,287
Current-period Gross writeoffs		31	1
Commercial [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans		246,307		231,011
Current-period Gross writeoffs		0	36
Commercial [Member] | New York and Other States [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Current-period Gross writeoffs	[2]	0	36
Commercial [Member] | Florida [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Current-period Gross writeoffs		0	0
Commercial [Member] | Commercial Real Estate [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		14,677		79,430
2022/2021		82,642		29,991
2021/2020		29,717		18,883
2020/2019		18,397		22,790
2019/2018		21,718		16,969
Prior		47,464		33,837
Revolving Loans Amortized Cost Basis		8,516		8,022
Revolving Loan Converted to Term		0		0
Total loans		223,131		209,922
2023/2022		0		0
2022/2021		0		0
2021/2020		0		0
2020/2019		0		0
2019/2018		0		0
Prior		0		40
Revolving Loans Amortized Cost Basis Writeoffs		0		0
Revolving Loan Converted to Term Writeoffs		0		0
Current-period Gross writeoffs		0		40
Commercial [Member] | Commercial Real Estate [Member] | New York and Other States [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans	[1]	182,287		177,371	[2]
Commercial [Member] | Commercial Real Estate [Member] | Florida [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans		40,844		32,551
Commercial [Member] | Commercial Real Estate [Member] | Pass [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		14,677		79,430
2022/2021		82,642		29,991
2021/2020		29,717		18,708
2020/2019		18,227		22,790
2019/2018		21,718		16,598
Prior		45,613		32,666
Revolving Loans Amortized Cost Basis		8,516		8,022
Revolving Loan Converted to Term		0		0
Total loans		221,110		208,205
Commercial [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		0		0
2022/2021		0		0
2021/2020		0		62
2020/2019		58		0
2019/2018		0		243
Prior		238		0
Revolving Loans Amortized Cost Basis		0		0
Revolving Loan Converted to Term		0		0
Total loans		296		305
Commercial [Member] | Commercial Real Estate [Member] | Substandard [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		0		0
2022/2021		0		0
2021/2020		0		113
2020/2019		112		0
2019/2018		0		128
Prior		1,613		1,171
Revolving Loans Amortized Cost Basis		0		0
Revolving Loan Converted to Term		0		0
Total loans		1,725		1,412
Commercial [Member] | Other [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		1,619		2,972
2022/2021		3,300		3,187
2021/2020		2,955		2,273
2020/2019		2,007		590
2019/2018		573		674
Prior		2,945		2,446
Revolving Loans Amortized Cost Basis		9,777		8,947
Revolving Loan Converted to Term		0		0
Total loans		23,176		21,089
2023/2022		0		0
2022/2021		0		0
2021/2020		0		0
2020/2019		0		0
2019/2018		0		0
Prior		0		0
Revolving Loans Amortized Cost Basis Writeoffs		0		0
Revolving Loan Converted to Term Writeoffs		0		0
Current-period Gross writeoffs		0		0
Commercial [Member] | Other [Member] | New York and Other States [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans	[1]	22,365		20,221	[2]
Commercial [Member] | Other [Member] | Florida [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans		811		868
Commercial [Member] | Other [Member] | Pass [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		1,619		2,972
2022/2021		3,300		2,848
2021/2020		2,617		2,273
2020/2019		2,007		590
2019/2018		573		674
Prior		2,847		2,348
Revolving Loans Amortized Cost Basis		9,739		8,908
Revolving Loan Converted to Term		0		0
Total loans		22,702		20,613
Commercial [Member] | Other [Member] | Special Mention [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		0		0
2022/2021		0		0
2021/2020		0		0
2020/2019		0		0
2019/2018		0		0
Prior		0		0
Revolving Loans Amortized Cost Basis		38		39
Revolving Loan Converted to Term		0		0
Total loans		38		39
Commercial [Member] | Other [Member] | Substandard [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		0		0
2022/2021		0		339
2021/2020		338		0
2020/2019		0		0
2019/2018		0		0
Prior		98		98
Revolving Loans Amortized Cost Basis		0		0
Revolving Loan Converted to Term		0		0
Total loans		436		437
Real Estate Mortgage - 1 to 4 Family [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans		4,537,949		4,489,883
Current-period Gross writeoffs		0	0
Real Estate Mortgage - 1 to 4 Family [Member] | New York and Other States [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Current-period Gross writeoffs	[2]	0	0
Real Estate Mortgage - 1 to 4 Family [Member] | Florida [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Current-period Gross writeoffs		0	0
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		87,414		557,981
2022/2021		576,805		934,250
2021/2020		921,875		784,592
2020/2019		772,219		368,981
2019/2018		362,201		258,277
Prior		1,462,877		1,241,349
Revolving Loans Amortized Cost Basis		1,360		1,472
Revolving Loan Converted to Term		0		0
Total loans		4,184,751		4,146,902
2023/2022		0		0
2022/2021		0		0
2021/2020		0		0
2020/2019		0		0
2019/2018		0		0
Prior		0		5
Revolving Loans Amortized Cost Basis Writeoffs		0		0
Revolving Loan Converted to Term Writeoffs		0		0
Current-period Gross writeoffs		0		5
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | New York and Other States [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans	[1]	2,760,159		2,776,989	[2]
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | Florida [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans		1,424,592		1,369,913
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | Performing [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		87,414		557,981
2022/2021		576,805		933,754
2021/2020		921,308		784,511
2020/2019		771,897		368,137
2019/2018		360,905		257,926
Prior		1,449,519		1,228,776
Revolving Loans Amortized Cost Basis		1,360		1,472
Revolving Loan Converted to Term		0		0
Total loans		4,169,208		4,132,557
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | Nonperforming [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		0		0
2022/2021		0		496
2021/2020		567		81
2020/2019		322		844
2019/2018		1,296		351
Prior		13,358		12,573
Revolving Loans Amortized Cost Basis		0		0
Revolving Loan Converted to Term		0		0
Total loans		15,543		14,345
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		2,103		6,863
2022/2021		6,750		9,124
2021/2020		8,828		6,322
2020/2019		6,205		7,588
2019/2018		7,313		5,306
Prior		25,509		21,346
Revolving Loans Amortized Cost Basis		0		0
Revolving Loan Converted to Term		0		0
Total loans		56,708		56,549
2023/2022		0		0
2022/2021		0		0
2021/2020		0		0
2020/2019		0		0
2019/2018		0		0
Prior		0		0
Revolving Loans Amortized Cost Basis Writeoffs		0		0
Revolving Loan Converted to Term Writeoffs		0		0
Current-period Gross writeoffs		0		0
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | New York and Other States [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans	[1]	44,112		43,999	[2]
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | Florida [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans		12,596		12,550
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | Performing [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		2,103		6,863
2022/2021		6,750		9,124
2021/2020		8,828		6,322
2020/2019		6,205		7,588
2019/2018		7,313		5,240
Prior		25,310		21,217
Revolving Loans Amortized Cost Basis		0		0
Revolving Loan Converted to Term		0		0
Total loans		56,509		56,354
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | Nonperforming [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		0		0
2022/2021		0		0
2021/2020		0		0
2020/2019		0		0
2019/2018		0		66
Prior		199		129
Revolving Loans Amortized Cost Basis		0		0
Revolving Loan Converted to Term		0		0
Total loans		199		195
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		52		1,369
2022/2021		509		1,253
2021/2020		441		740
2020/2019		101		52
2019/2018		39		100
Prior		18,653		20,488
Revolving Loans Amortized Cost Basis		276,695		262,430
Revolving Loan Converted to Term		0		0
Total loans		296,490		286,432
2023/2022		0		0
2022/2021		0		0
2021/2020		0		0
2020/2019		0		0
2019/2018		0		0
Prior		0		19
Revolving Loans Amortized Cost Basis Writeoffs		0		0
Revolving Loan Converted to Term Writeoffs		0		0
Current-period Gross writeoffs		0		19
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | New York and Other States [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans	[1]	193,645		191,926	[2]
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | Florida [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans		102,845		94,506
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | Performing [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		52		1,369
2022/2021		509		1,246
2021/2020		434		740
2020/2019		101		52
2019/2018		39		100
Prior		16,510		18,377
Revolving Loans Amortized Cost Basis		276,428		262,244
Revolving Loan Converted to Term		0		0
Total loans		294,073		284,128
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | Nonperforming [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		0		0
2022/2021		0		7
2021/2020		7		0
2020/2019		0		0
2019/2018		0		0
Prior		2,143		2,111
Revolving Loans Amortized Cost Basis		267		186
Revolving Loan Converted to Term		0		0
Total loans		2,417		2,304
Installment [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		3,780		6,405
2022/2021		6,300		2,512
2021/2020		2,243		805
2020/2019		671		774
2019/2018		592		374
Prior		636		309
Revolving Loans Amortized Cost Basis		1,104		1,128
Revolving Loan Converted to Term		0		0
Total loans		15,326		12,307
2023/2022		0		1
2022/2021		24		47
2021/2020		7		22
2020/2019		5		7
2019/2018		0		2
Prior		12		9
Revolving Loans Amortized Cost Basis Writeoffs		0		0
Revolving Loan Converted to Term Writeoffs		0		0
Current-period Gross writeoffs		48	11	88
Installment [Member] | New York and Other States [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans	[1]	11,484		9,408	[2]
Current-period Gross writeoffs	[2]	17	10
Installment [Member] | Florida [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Total loans		3,842		2,899
Current-period Gross writeoffs		31	$ 1
Installment [Member] | Performing [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		3,780		6,385
2022/2021		6,300		2,495
2021/2020		2,190		805
2020/2019		671		709
2019/2018		528		374
Prior		636		308
Revolving Loans Amortized Cost Basis		1,100		1,125
Revolving Loan Converted to Term		0		0
Total loans		15,205		12,201
Installment [Member] | Nonperforming [Member]
Credit Risk Profile, Segregated by Class [Abstract]
2023/2022		0		20
2022/2021		0		17
2021/2020		53		0
2020/2019		0		65
2019/2018		64		0
Prior		0		1
Revolving Loans Amortized Cost Basis		4		3
Revolving Loan Converted to Term		0		0
Total loans		$ 121		$ 106

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

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