Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2019
Provision (benefit) for credit losses	$ (6,926)	$ 2,470	$ (5,642)	$ 19,206
Allowance for credit losses	36,363	38,343	$ 36,363	38,343	$ 45,153	$ 42,670	$ 36,710	$ 21,751
Percentage of financing receivable on total loans			0.55%		0.67%
Percentage of financing receivable non-performing loans			179.90%		214.30%
Loans Receivable [Member]
Interest Receivable	38,000		$ 38,000		$ 41,500
Commercial Real Estate
Provision (benefit) for credit losses	(112)	1,576	(2,507)	2,948
Allowance for credit losses	5,756	8,547	5,756	8,547	8,327	5,868	6,971	4,429
Multi-family Residential Portfolio Segment [Member]
Provision (benefit) for credit losses	(161)	(1,553)	(126)	2,628
Allowance for credit losses	6,398	7,396	6,398	7,396	6,557	6,559	8,935	5,391
Taxi Medallion Portfolio Segment [Member]
Provision (benefit) for credit losses	(1,235)	951	1,301	951
Taxi Medallion Portfolio Segment [Member] | Performing Financial Instruments [Member]
Non-accrual loans					400
Commercial Business and Other Portfolio Segment [Member]
Provision (benefit) for credit losses	(4,354)	2,702	(2,334)	12,317
Allowance for credit losses	$ 20,300	$ 17,941	$ 20,300	$ 17,941	24,666	$ 25,548	$ 15,248	$ 8,554
Commercial Business and Other Portfolio Segment [Member] | Performing Financial Instruments [Member]
Non-accrual loans					$ 2,200