Loans - Troubled Debt Restructurings That Are Performing (Details)	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) contract	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) contract
Number of contracts	1	2	1
Performing Financial Instruments [Member]
Number of contracts | contract		19		25
Amortized Cost		$ 13,137,000		$ 15,911,000
Multi-Family Residential [Member] | Performing Financial Instruments [Member]
Number of contracts | contract		6		6
Amortized Cost		$ 1,681,000		$ 1,700,000
Commercial Real Estate | Performing Financial Instruments [Member]
Number of contracts | contract		1		1
Amortized Cost		$ 7,572,000		$ 7,702,000
One-To-Four Family - Mixed Used Property [Member]
Number of contracts	1		1
One-To-Four Family - Mixed Used Property [Member] | Performing Financial Instruments [Member]
Number of contracts | contract		5		5
Amortized Cost		$ 1,655,000		$ 1,731,000
One-To-Four Family - Residential [Member] | Performing Financial Instruments [Member]
Number of contracts | contract		3		3
Amortized Cost		$ 489,000		$ 507,000
Taxi Medallion Portfolio Segment [Member] | Performing Financial Instruments [Member]
Number of contracts | contract				2
Amortized Cost				$ 440,000
Commercial Business and Other [Member]
Number of contracts		2
Commercial Business and Other [Member] | Performing Financial Instruments [Member]
Number of contracts | contract		4		8
Amortized Cost		$ 1,740,000		$ 3,831,000