Loans and Allowance for Loan Losses - Non-performing Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Loans ninety days or more past due and still accruing	$ 2,748	$ 445
Non-accrual loans		12,813
Total non-performing loans		13,258
Mortgage Receivable [Member]
Non-accrual loans		8,076
Non-Mortgage Loans [Member]
Non-accrual loans		4,737
Multi-family Residential Portfolio Segment [Member]
Loans ninety days or more past due and still accruing	201
Multi-family Residential Portfolio Segment [Member] | Mortgage Receivable [Member]
Non-accrual loans		2,296
Commercial Real Estate
Loans ninety days or more past due and still accruing	2,547	445
Commercial Real Estate | Mortgage Receivable [Member]
Non-accrual loans		367
One-To-Four Family - Mixed-Use Property Portfolio Segment [Member] | Mortgage Receivable [Member]
Non-accrual loans		274
One-To-Four Family - Residential Portfolio Segment [Member] | Mortgage Receivable [Member]
Non-accrual loans		5,139
Small Business Administration Portfolio Segment [Member] | Non-Mortgage Loans [Member]
Non-accrual loans		1,151
Taxi Medallion Portfolio Segment [Member] | Non-Mortgage Loans [Member]
Non-accrual loans		1,641
Commercial Business and Other Portfolio Segment [Member] | Non-Mortgage Loans [Member]
Non-accrual loans		$ 1,945
Performing Financial Instruments [Member] | One-To-Four Family - Mixed-Use Property Portfolio Segment [Member]
Non-accrual loans	300
Performing Financial Instruments [Member] | Taxi Medallion Portfolio Segment [Member]
Non-accrual loans	400
Performing Financial Instruments [Member] | Commercial Business and Other Portfolio Segment [Member]
Non-accrual loans	$ 2,200