Note 5 - Loans - Troubled Debt Restructurings That Are Not Performing According to Their Restructured Terms (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0
Nonperforming Financial Instruments [Member]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	1	1
Recorded investment, not performing	$ 383	$ 383
Multi-family Residential Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	1	1
Recorded investment, not performing	$ 383	$ 383