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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income	$ 9,306	$ 9,100	$ 9,066	$ 8,868	$ 1,213	$ 7,652	$ 6,418	$ 6,202	$ 36,340	$ 21,485	$ 25,126
Weighted average common shares outstanding, basic (in shares)	16,201,148	16,512,823	16,689,398	16,955,758	16,992,519	17,005,654	17,012,189	16,998,125	16,587,504	17,002,116	17,319,689
Total dilutive effect of potential common shares (in shares)									78,881	75,726	45,835
Weighted average common shares outstanding, diluted (in shares)	16,280,404	16,612,416	16,788,615	17,047,638	17,083,949	17,082,729	17,082,832	17,072,174	16,666,385	17,077,842	17,365,524
Basic earnings per common share (in dollars per share)	$ 0.58	$ 0.55	$ 0.54	$ 0.52	$ 0.07	$ 0.45	$ 0.38	$ 0.36	$ 2.19	$ 1.26	$ 1.45
Diluted earnings per common share (in dollars per share)	$ 0.57	$ 0.55	$ 0.54	$ 0.52	$ 0.07	$ 0.45	$ 0.38	$ 0.36	$ 2.18	$ 1.26	$ 1.45
Antidilutive potential common shares (in shares)									2,755	67,701	110,871
Employee Stock Option [Member]
Dilutive effect of potential common shares (in shares)									62,417	52,205	34,530
Antidilutive potential common shares (in shares)									19	64,081	107,592
Restricted Stock [Member]
Dilutive effect of potential common shares (in shares)									16,464	23,521	11,305
Antidilutive potential common shares (in shares)									2,736	3,620	3,279