Note 3 - Investment Securities Available for Sale - Investment Securities With Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Less than 12 months fair value	$ 998	$ 13,284
Less than 12 months unrealized losses	1	60
12 months or more fair value		19,733
12 months or more unrealized losses		155
Total fair value	998	33,017
Total unrealized losses	1	215
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Less than 12 months fair value		10,319
Less than 12 months unrealized losses		31
12 months or more fair value		19,733
12 months or more unrealized losses		155
Total fair value		30,052
Total unrealized losses		186
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months fair value	998	2,965
Less than 12 months unrealized losses	1	29
12 months or more fair value
12 months or more unrealized losses
Total fair value	998	2,965
Total unrealized losses	$ 1	$ 29