Loans - Age Analysis of Recorded Investment in Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Loans, Past Due	$ 43,390	$ 67,381
Loans, Current	6,586,964	6,637,293
Loans	6,630,354	6,704,674
Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	22,144	36,947
Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	1,514	11,519
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	19,732	18,915
Multi-family Residential Portfolio Segment [Member]
Loans, Past Due	20,914	13,545
Loans, Current	2,480,107	2,522,432
Loans	2,501,021	2,535,977
Multi-family Residential Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	16,453	7,582
Multi-family Residential Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	0	3,186
Multi-family Residential Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	4,461	2,777
Commercial Real Estate
Loans, Past Due	2,597	27,339
Loans, Current	1,745,136	1,731,045
Loans	1,747,733	1,758,384
Commercial Real Estate | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	1,119	17,903
Commercial Real Estate | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	838	5,123
Commercial Real Estate | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	640	4,313
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member]
Loans, Past Due	4,075	8,238
Loans, Current	578,268	598,647
Loans	582,343	606,885
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	1,657	5,673
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	172	1,132
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	2,246	1,433
One-To-Four Family - Residential Portfolio Segment [Member]
Loans, Past Due	8,385	9,205
Loans, Current	280,858	243,486
Loans	289,243	252,691
One-To-Four Family - Residential Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	372	3,087
One-To-Four Family - Residential Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	504	805
One-To-Four Family - Residential Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	7,509	5,313
Construction Portfolio Segment [Member]
Loans, Past Due	873	750
Loans, Current	70,495	82,411
Loans	71,368	83,161
Construction Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	0	750
Construction Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	0	0
Construction Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	873	0
Small Business Administration Portfolio Segment [Member]
Loans, Past Due	4,128	2,991
Loans, Current	141,506	162,579
Loans	145,634	165,570
Small Business Administration Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	2,085	1,823
Small Business Administration Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	0	0
Small Business Administration Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	2,043	1,168
Taxi Medallion Portfolio Segment [Member]
Loans, Past Due	0	2,318
Loans, Current	0	279
Loans	0	2,597
Taxi Medallion Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	0	0
Taxi Medallion Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	0	0
Taxi Medallion Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	0	2,318
Commercial Business and Other Portfolio Segment [Member]
Loans, Past Due	2,418	2,995
Loans, Current	1,290,594	1,296,414
Loans	1,293,012	1,299,409
Commercial Business and Other Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	458	129
Commercial Business and Other Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	0	1,273
Commercial Business and Other Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	$ 1,960	$ 1,593