Loans and Allowance for Loan Losses - Composition of Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Loans	$ 6,701,629	$ 5,756,935
Net unamortized premiums and unearned loan fees	3,045	15,271
Aggregate outstanding loans	6,704,674	5,772,206
Multi-Family Residential [Member]
Loans	2,533,952	2,238,591
Commercial Real Estate Loans [Member]
Loans	1,754,754	1,582,008
One-To-Four Family - Mixed Used Property [Member]
Loans	602,981	592,471
One-To-Four Family - Residential [Member]
Loans	245,211	188,216
Co-Operative Apartments [Member]
Loans	8,051	8,663
Construction Portfolio Segment [Member]
Loans	83,322	67,754
Aggregate outstanding loans	83,161
Small Business Administration [Member]
Loans	167,376	14,445
Small Business Administration [Member] \| Small Business Administration, Cares Act, Paycheck Protection Program
Loans	151,900
Taxi Medallion [Member]
Loans	2,757	3,309
Commercial Business and Other [Member]
Loans	$ 1,303,225	$ 1,061,478

Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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