Note 16 - Accumulated Other Comprehensive Income - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
(Losses) gains recognized	$ 0	$ 0	$ 0	$ 385	$ 0	$ 0	$ (43)	$ 0	$ 385	$ (43)	$ (618)
Income before income taxes	14,939	10,598	10,508	10,067	12,397	11,736	13,402	12,261	46,112	49,796	45,122
Income tax benefit	3,389	2,332	2,270	2,195	2,833	2,580	2,951	2,630	10,186	10,994	8,782
Net income	$ 11,550	$ 8,266	$ 8,238	$ 7,872	$ 9,564	$ 9,156	$ 10,451	$ 9,631	35,926	38,802	36,340
Reclassification out of Accumulated Other Comprehensive Income [Member]
(Losses) gains recognized									(385)	43	618
Income tax benefit									81	(9)	(130)
Net income									0	254	713
Reclassification out of Accumulated Other Comprehensive Income [Member] | AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Income before income taxes									(385)	43	618
Income tax benefit									(82)	(58)	(60)
Net income									(304)	34	488
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Other operating expense									201	257	228
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Other operating expense									185	21	57
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Income before income taxes									386	278	285
Net income									$ 304	$ 220	$ 225