Loans and Allowance for Loan Losses, Risk Category of Loans (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Loans and Leases Receivable [Abstract]
Total loans, net		$ 3,825,916	$ 3,636,407
Non-accrual loans included in classified loans		2,000	1,500
New York and Other States [Member]
Loans and Leases Receivable [Abstract]
Total loans, net	[1]	2,914,396	2,795,993
Florida [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		911,520	840,414
Commercial [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		190,987	186,207
Commercial [Member] | New York and Other States [Member]
Loans and Leases Receivable [Abstract]
Total loans, net	[1]	178,452	172,974
Commercial [Member] | Florida [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		12,535	13,233
Commercial [Member] | Pass [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		184,512	175,857
Commercial [Member] | Pass [Member] | New York and Other States [Member]
Loans and Leases Receivable [Abstract]
Total loans, net	[1]	172,091	162,742
Commercial [Member] | Pass [Member] | Florida [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		12,421	13,115
Commercial [Member] | Classified [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		6,475	10,350
Commercial [Member] | Classified [Member] | New York and Other States [Member]
Loans and Leases Receivable [Abstract]
Total loans, net	[1]	6,361	10,232
Commercial [Member] | Classified [Member] | Florida [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		114	118
Commercial [Member] | Commercial Real Estate [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		166,487	161,892
Commercial [Member] | Commercial Real Estate [Member] | New York and Other States [Member]
Loans and Leases Receivable [Abstract]
Total loans, net	[1]	154,206	149,368
Commercial [Member] | Commercial Real Estate [Member] | Florida [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		12,281	12,524
Commercial [Member] | Commercial Real Estate [Member] | Pass [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		161,197	153,212
Commercial [Member] | Commercial Real Estate [Member] | Pass [Member] | New York and Other States [Member]
Loans and Leases Receivable [Abstract]
Total loans, net	[1]	149,030	140,806
Commercial [Member] | Commercial Real Estate [Member] | Pass [Member] | Florida [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		12,167	12,406
Commercial [Member] | Commercial Real Estate [Member] | Classified [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		5,290	8,680
Commercial [Member] | Commercial Real Estate [Member] | Classified [Member] | New York and Other States [Member]
Loans and Leases Receivable [Abstract]
Total loans, net	[1]	5,176	8,562
Commercial [Member] | Commercial Real Estate [Member] | Classified [Member] | Florida [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		114	118
Commercial [Member] | Other [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		24,500	24,315
Commercial [Member] | Other [Member] | New York and Other States [Member]
Loans and Leases Receivable [Abstract]
Total loans, net	[1]	24,246	23,606
Commercial [Member] | Other [Member] | Florida [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		254	709
Commercial [Member] | Other [Member] | Pass [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		23,315	22,645
Commercial [Member] | Other [Member] | Pass [Member] | New York and Other States [Member]
Loans and Leases Receivable [Abstract]
Total loans, net	[1]	23,061	21,936
Commercial [Member] | Other [Member] | Pass [Member] | Florida [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		254	709
Commercial [Member] | Other [Member] | Classified [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		1,185	1,670
Commercial [Member] | Other [Member] | Classified [Member] | New York and Other States [Member]
Loans and Leases Receivable [Abstract]
Total loans, net	[1]	1,185	1,670
Commercial [Member] | Other [Member] | Classified [Member] | Florida [Member]
Loans and Leases Receivable [Abstract]
Total loans, net		$ 0	$ 0

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