Note 2 - Investment Securities - Amortized Cost and Fair Value of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Securities available for sale, amortized cost, due in one year or less	$ 4,145
Securities available for sale, fair value, due in one year or less	4,148
Securities held to maturity, amortized cost, due in one year or less	0
Securities held to maturity, fair value, due in one year or less	0
Securities available for sale, amortized cost, due after one year through five years	77,109
Securities available for sale, fair value, due after one year through five years	76,737
Securities held to maturity, amortized cost, due after one year through five years	0
Securities held to maturity, fair value, due after one year through five years	0
Securities available for sale, amortized cost, due after five years through ten years	27,808
Securities available for sale, fair value, due after five years through ten years	27,991
Securities held to maturity, amortized cost, due after five years through ten years
Securities held to maturity, fair value, due after five years through ten years
Securities available for sale, amortized cost, due after ten years	33,620
Securities available for sale, fair value, due after ten years	34,507
Securities held to maturity, amortized cost, due after ten years	0
Securities held to maturity, fair value, due after ten years	0
Securities available for sale, amortized cost, singal maturity	142,682
Securities available for sale, fair value, singal maturity	143,383
Securities held to maturity, amortized cost, singal maturity	0
Securities held to maturity, fair value, singal maturity	0
Securities available for sale, amortized cost, mortgage-backed securities and CMO	134,862
Securities available for sale, fair value, mortgage-backed securities and CMO	133,343
Securities held to maturity, amortized cost, mortgage-backed securities and CMO	1
Securities held to maturity, fair value, mortgage-backed securities and CMO	1
Securities held to maturity, amortized cost	1	$ 2
Securities held to maturity, fair value	1	$ 2
Debt Securities [Member]
Securities available for sale, amortized cost	277,544
Securities available for sale, fair value	276,726
Securities held to maturity, amortized cost	1
Securities held to maturity, fair value	$ 1