Note 3 - Securities - Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Due in one year or less, available for sale, amortized cost
Due in one year or less, available for sale, fair value
Due in one year or less, held to maturity, amortized cost	2,128
Due in one year or less, held to maturity, fair value	2,148
Due in over one to five years, available for sale, amortized cost	14,888
Due in over one to five years, available for sale, fair value	14,588
Due in over one to five years, held to maturity, amortized cost	5,814
Due in over one to five years, held to maturity, fair value	5,994
Due in over five to ten years, available for sale, amortized cost
Due in over five to ten years, available for sale, fair value
Due in over five to ten years, held to maturity, amortized cost	7,109
Due in over five to ten years, held to maturity, fair value	7,419
Due after ten years, available for sale, amortized cost
Due after ten years, available for sale, fair value
Due after ten years, held to maturity, amortized cost	2,259
Due after ten years, held to maturity, fair value	2,188
Agency mortgage-backed securities, residential, available for sale, amortized cost	88,581
Agency mortgage-backed securities, residential, available for sale, fair value	85,577
Agency mortgage-backed securities, residential, held to maturity, amortized cost	3
Agency mortgage-backed securities, residential, held to maturity, fair value	3
Total debt securities, available for sale, amortized cost	103,469	$ 102,455
Total debt securities, available for sale, fair value	100,165	101,125
Total debt securities, held to maturity, amortized cost	17,313	17,581
Total debt securities, held to maturity, fair value	$ 17,752	$ 18,079