Note 3 - Investment Securities Available for Sale - Investment Securities With Unrealized Losses (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
12 months or more unrealized losses	$ 57	$ 70
Total fair value	66,691	88,433
Total unrealized losses	959	1,754
Less than 12 months fair value	64,846	86,390
Less than 12 months unrealized losses	902	1,684
12 months or more fair value	1,845	2,043
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
12 months or more unrealized losses	57	70
Total fair value	60,145	70,381
Total unrealized losses	821	1,307
Less than 12 months fair value	58,300	68,338
Less than 12 months unrealized losses	764	1,237
12 months or more fair value	1,845	2,043
US States and Political Subdivisions Debt Securities [Member]
12 months or more unrealized losses
Total fair value	6,546	18,052
Total unrealized losses	138	447
Less than 12 months fair value	6,546	18,052
Less than 12 months unrealized losses	138	447
12 months or more fair value