Note 3 - Investment Securities Available for Sale - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Within one year, Amortized Cost
Within one year, Estimated Fair Value
After one year through five years, Amortized cost	2,842
After one year through five years, Estimated fair value	2,891
After five years through ten years, Amortized cost	16,639
After five years through ten years, Estimated fair value	16,930
After ten years, Amortized cost	12,065
After ten years, Estimated fair value	12,092
Total , Amortized cost	112,683	$ 103,249
Total , Estimated fair value	112,329	101,595
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Government-sponsored mortgage-backed securities, Amortized cost	81,137
Government-sponsored mortgage-backed securities, Estimated fair value	80,416
Total , Amortized cost	81,137	76,207
Total , Estimated fair value	$ 80,416	$ 74,911