Loans and Allowance for Loan Losses, Past Due (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2018	Dec. 31, 2017
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		$ 22,384	$ 22,272
Current		3,803,532	3,614,135
Total loans		3,825,916	3,636,407
Loans that are 90 days past due and still accruing interest		$ 0	$ 0
Number of days past due		90 days	90 days
New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	$ 20,476	$ 20,557
Current	[1]	2,893,920	2,775,436
Total loans	[1]	2,914,396	2,795,993
Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		1,908	1,715
Current		909,612	838,699
Total loans		911,520	840,414
30-59 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		4,422	6,673
30-59 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	3,808	6,393
30-59 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		614	280
60-89 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		2,058	1,514
60-89 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	1,874	1,509
60-89 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		184	5
90+ Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		15,904	14,085
90+ Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	14,794	12,655
90+ Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		1,110	1,430
Commercial [Member]
Aging of the recorded investment in past due loans [Abstract]
Total loans		190,987	186,207
Commercial [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total loans	[1]	178,452	172,974
Commercial [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total loans		12,535	13,233
Commercial [Member] | Commercial Real Estate [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		546	1,689
Current		165,941	160,203
Total loans		166,487	161,892
Commercial [Member] | Commercial Real Estate [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	546	1,689
Current	[1]	153,660	147,679
Total loans	[1]	154,206	149,368
Commercial [Member] | Commercial Real Estate [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Current		12,281	12,524
Total loans		12,281	12,524
Commercial [Member] | Commercial Real Estate [Member] | 30-59 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	183
Commercial [Member] | Commercial Real Estate [Member] | 30-59 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	0	183
Commercial [Member] | Commercial Real Estate [Member] | 30-59 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Commercial [Member] | Commercial Real Estate [Member] | 60-89 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		111	174
Commercial [Member] | Commercial Real Estate [Member] | 60-89 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	111	174
Commercial [Member] | Commercial Real Estate [Member] | 60-89 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Commercial [Member] | Commercial Real Estate [Member] | 90+ Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		435	1,332
Commercial [Member] | Commercial Real Estate [Member] | 90+ Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	435	1,332
Commercial [Member] | Commercial Real Estate [Member] | 90+ Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Commercial [Member] | Other [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		274	100
Current		24,226	24,215
Total loans		24,500	24,315
Commercial [Member] | Other [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	274	100
Current	[1]	23,972	23,506
Total loans	[1]	24,246	23,606
Commercial [Member] | Other [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Current		254	709
Total loans		254	709
Commercial [Member] | Other [Member] | 30-59 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Commercial [Member] | Other [Member] | 30-59 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	0	0
Commercial [Member] | Other [Member] | 30-59 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Commercial [Member] | Other [Member] | 60-89 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Commercial [Member] | Other [Member] | 60-89 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	0	0
Commercial [Member] | Other [Member] | 60-89 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Commercial [Member] | Other [Member] | 90+ Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		274	100
Commercial [Member] | Other [Member] | 90+ Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	274	100
Commercial [Member] | Other [Member] | 90+ Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Real Estate Mortgage - 1 to 4 Family [Member]
Aging of the recorded investment in past due loans [Abstract]
Total loans		3,624,962	3,441,437
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		18,539	17,664
Current		3,225,672	3,034,413
Total loans		3,244,211	3,052,077
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	16,781	15,983
Current	[1]	2,392,165	2,270,165
Total loans	[1]	2,408,946	2,286,148
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		1,758	1,681
Current		833,507	764,248
Total loans		835,265	765,929
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | 30-59 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		3,709	5,946
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | 30-59 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	3,177	5,669
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | 30-59 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		532	277
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | 60-89 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		1,775	1,300
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | 60-89 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	1,596	1,300
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | 60-89 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		179	0
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | 90+ Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		13,055	10,418
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | 90+ Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	12,008	9,014
Real Estate Mortgage - 1 to 4 Family [Member] | First Mortgages [Member] | 90+ Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		1,047	1,404
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		231	51
Current		86,770	80,393
Total loans		87,001	80,444
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	180	51
Current	[1]	70,734	66,404
Total loans	[1]	70,914	66,455
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		51	0
Current		16,036	13,989
Total loans		16,087	13,989
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | 30-59 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		68	6
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | 30-59 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	17	6
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | 30-59 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		51	0
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | 60-89 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | 60-89 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	0	0
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | 60-89 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | 90+ Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		163	45
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | 90+ Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	163	45
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Loans [Member] | 90+ Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		2,693	2,646
Current		291,057	306,270
Total loans		293,750	308,916
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	2,614	2,646
Current	[1]	245,660	260,629
Total loans	[1]	248,274	263,275
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		79	0
Current		45,397	45,641
Total loans		45,476	45,641
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | 30-59 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		598	489
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | 30-59 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	569	489
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | 30-59 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		29	0
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | 60-89 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		141	18
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | 60-89 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	141	18
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | 60-89 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		0	0
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | 90+ Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		1,954	2,139
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | 90+ Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	1,904	2,139
Real Estate Mortgage - 1 to 4 Family [Member] | Home Equity Lines of Credit [Member] | 90+ Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		50	0
Installment [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		101	122
Current		9,866	8,641
Total loans		9,967	8,763
Installment [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	81	88
Current	[1]	7,729	7,053
Total loans	[1]	7,810	7,141
Installment [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		20	34
Current		2,137	1,588
Total loans		2,157	1,622
Installment [Member] | 30-59 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		47	49
Installment [Member] | 30-59 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	45	46
Installment [Member] | 30-59 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		2	3
Installment [Member] | 60-89 Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		31	22
Installment [Member] | 60-89 Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	26	17
Installment [Member] | 60-89 Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		5	5
Installment [Member] | 90+ Days Past Due [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		23	51
Installment [Member] | 90+ Days Past Due [Member] | New York and Other States [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due	[1]	10	25
Installment [Member] | 90+ Days Past Due [Member] | Florida [Member]
Aging of the recorded investment in past due loans [Abstract]
Total 30+ days Past Due		$ 13	$ 26

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