Note 18 - Earnings Per Share - Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income	$ 9,564	$ 9,156	$ 10,451	$ 9,631	$ 9,306	$ 9,100	$ 9,066	$ 8,868	$ 38,802	$ 36,340	$ 21,485
Weighted average common shares outstanding, basic (in shares)	15,611,093	15,603,992	15,712,204	15,839,424	16,201,148	16,512,823	16,689,398	16,955,758	15,690,812	16,587,504	17,002,116
Total dilutive effect of potential common shares (in shares)									65,281	78,881	75,726
Weighted average common shares outstanding, diluted (in shares)	15,670,047	15,664,587	15,775,320	15,920,950	16,280,404	16,612,416	16,788,615	17,047,638	15,756,093	16,666,385	17,077,842
Basic earnings per common share (in dollars per share)	$ 0.61	$ 0.59	$ 0.67	$ 0.61	$ 0.58	$ 0.55	$ 0.54	$ 0.52	$ 2.47	$ 2.19	$ 1.26
Diluted earnings per common share (in dollars per share)	$ 0.61	$ 0.58	$ 0.66	$ 0.60	$ 0.57	$ 0.55	$ 0.54	$ 0.52	$ 2.46	$ 2.18	$ 1.26
Antidilutive potential common shares (in shares)									25,878	2,755	67,701
Share-based Payment Arrangement, Option [Member]
Dilutive effect of potential common shares (in shares)									53,907	62,417	52,205
Antidilutive potential common shares (in shares)									25	19	64,081
Restricted Stock [Member]
Dilutive effect of potential common shares (in shares)									11,374	16,464	23,521
Antidilutive potential common shares (in shares)									25,853	2,736	3,620