Note 2 - Investment Securities - Unrealized Loss Positions of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
US Government Agencies Debt Securities [Member]
Securities available-for-sale in a continuous unrealized loss position, less than 12 months fair value	$ 692	$ 1,999
Securities available-for-sale in a continuous unrealized loss position, less than 12 months unrealized loss	(1)	(24)
Securities available-for-sale in a continuous unrealized loss position, 12 months or more fair value	3,799	4,924
Securities available-for-sale in a continuous unrealized loss position, 12 months or more unrealized loss	(39)	(83)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	4,491	6,923
Securities available-for-sale in a continuous unrealized loss position, total unrealized loss	(40)	(107)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale in a continuous unrealized loss position, less than 12 months fair value	280	10,326
Securities available-for-sale in a continuous unrealized loss position, less than 12 months unrealized loss	(2)	(114)
Securities available-for-sale in a continuous unrealized loss position, 12 months or more fair value	1,703	3,069
Securities available-for-sale in a continuous unrealized loss position, 12 months or more unrealized loss	(26)	(60)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,983	13,395
Securities available-for-sale in a continuous unrealized loss position, total unrealized loss	(28)	(174)
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale in a continuous unrealized loss position, less than 12 months fair value	863	805
Securities available-for-sale in a continuous unrealized loss position, less than 12 months unrealized loss	(11)	(10)
Securities available-for-sale in a continuous unrealized loss position, 12 months or more fair value	270	526
Securities available-for-sale in a continuous unrealized loss position, 12 months or more unrealized loss		(5)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,133	1,331
Securities available-for-sale in a continuous unrealized loss position, total unrealized loss	(11)	(15)
Securities available-for-sale in a continuous unrealized loss position, less than 12 months fair value	1,835	13,130
Securities available-for-sale in a continuous unrealized loss position, less than 12 months unrealized loss	(14)	(148)
Securities available-for-sale in a continuous unrealized loss position, 12 months or more fair value	5,772	8,519
Securities available-for-sale in a continuous unrealized loss position, 12 months or more unrealized loss	(65)	(148)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	7,607	21,649
Securities available-for-sale in a continuous unrealized loss position, total unrealized loss	$ (79)	$ (296)