Note 3 - Investment Securities - Investment Securities With Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Less than 12 months fair value	$ 681	$ 45,748
Less than 12 months unrealized losses	10	553
12 months or more fair value	95,118	83,148
12 months or more unrealized losses	1,460	2,671
Total fair value	95,799	128,896
Total unrealized losses	1,470	3,224
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Less than 12 months fair value		26,478
Less than 12 months unrealized losses		269
12 months or more fair value	84,580	77,476
12 months or more unrealized losses	1,320	2,352
Total fair value	84,580	103,954
Total unrealized losses	1,320	2,621
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months fair value	681	19,270
Less than 12 months unrealized losses	10	284
12 months or more fair value	10,538	5,672
12 months or more unrealized losses	140	319
Total fair value	11,219	24,942
Total unrealized losses	$ 150	$ 603