Note 5 - Loans - Troubled Debt Restructurings That Are Not Performing According to Their Restructured Terms (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019 USD ($)	Sep. 30, 2018	Dec. 31, 2018 USD ($)
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts	0	0	0	0
Nonperforming Financial Instruments [Member]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts			5		2
Recorded investment, not performing			$ 1,046		$ 1,785
Multi-family Residential Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts			0		1
Recorded investment, not performing			$ 0		$ 388
Taxi Medallion Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts			3		0
Recorded investment, not performing			$ 767		$ 0
Commercial Business and Other Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts			2		1
Recorded investment, not performing			$ 279		$ 1,397