Loans Receivable - Loan Origination and Risk Management (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, amount	$ 1,154,892	$ 1,174,728
Multi-family mortgage loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, amount	542,421	563,750
Nonresidential Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, amount	133,432	134,674
Commercial leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases, amount	$ 266,063	$ 272,629