Loans and Allowance for Loan Losses - Age Analysis of Recorded Investment in Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Loans, Past Due	$ 63,007	$ 28,928
Loans, Current	5,920,268	5,728,007
Total Loans	5,983,275	5,756,935
Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	31,597	8,219
Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	12,195	8,027
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	19,215	12,682
Multi-family Residential Portfolio Segment [Member]
Loans, Past Due	15,720	8,346
Loans, Current	2,276,642	2,230,245
Total Loans	2,292,362	2,238,591
Multi-family Residential Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	10,700	4,042
Multi-family Residential Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	1,292	1,563
Multi-family Residential Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	3,728	2,741
Commercial Real Estate Portfolio Segment [Member]
Loans, Past Due	13,686	5,308
Loans, Current	1,635,564	1,576,700
Total Loans	1,649,250	1,582,008
Commercial Real Estate Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	9,727	0
Commercial Real Estate Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	1,259	4,941
Commercial Real Estate Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	2,700	367
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member]
Loans, Past Due	10,651	1,887
Loans, Current	585,053	590,584
Total Loans	595,704	592,471
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	6,851	1,117
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	1,252	496
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	2,548	274
One-To-Four Family - Residential Portfolio Segment [Member]
Loans, Past Due	12,548	6,881
Loans, Current	182,244	181,335
Total Loans	194,792	188,216
One-To-Four Family - Residential Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	3,337	720
One-To-Four Family - Residential Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	3,342	1,022
One-To-Four Family - Residential Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	5,869	5,139
Co-Operative Apartments Portfolio Segment [Member]
Loans, Past Due		0
Loans, Current		8,663
Total Loans		8,663
Co-Operative Apartments Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due		0
Co-Operative Apartments Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due		0
Co-Operative Apartments Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due		0
Construction Portfolio Segment [Member]
Loans, Past Due	0	0
Loans, Current	69,257	67,754
Total Loans	69,257	67,754
Construction Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	0	0
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	0	0
Small Business Administration Portfolio Segment [Member]
Loans, Past Due	1,613	1,151
Loans, Current	103,855	13,294
Total Loans	105,468	14,445
Small Business Administration Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	0	0
Small Business Administration Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	266	0
Small Business Administration Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	1,347	1,151
Taxi Medallion Portfolio Segment [Member]
Loans, Past Due	1,195	1,065
Loans, Current	2,075	2,244
Total Loans	3,270	3,309
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	1,195	1,065
Commercial Business and Other Portfolio Segment [Member]
Loans, Past Due	7,594	4,290
Loans, Current	1,065,578	1,057,188
Total Loans	1,073,172	1,061,478
Commercial Business and Other Portfolio Segment [Member] | Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, Past Due	982	2,340
Commercial Business and Other Portfolio Segment [Member] | Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, Past Due	4,784	5
Commercial Business and Other Portfolio Segment [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, Past Due	$ 1,828	$ 1,945