Note 11 - Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Provision For Income Taxes [Abstract]
Current Federal income taxes									$ 3,454	$ 3,137	$ 2,519
Current state income taxes									124	62	51
Deferred Federal income taxes (benefits)									268	(145)	0
Net provision prior to tax reform adjustment									3,846	3,054	2,570
DTA writeoff for change in tax rate under 2017 Tax Reform									2,054	0	0
Net provision	$ 2,993	$ 940	$ 845	$ 1,122	$ 743	$ 821	$ 702	$ 788	$ 5,900	$ 3,054	$ 2,570