Note 18 - Earnings per Share - Basic and Diluted (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
Earnings Per Share
Net income	$ 15,891	$ 15,095	$ 13,504	$ 12,918	$ 13,316	$ 8,809	$ 10,445	$ 10,550	$ 57,408	$ 43,120	$ 35,707
Basic EPS	$ 1.01	$ 0.96	$ 0.86	$ 0.82	$ 0.85	$ 0.56	$ 0.75	$ 0.76	$ 3.65	$ 2.92	$ 2.68
Diluted EPS	$ 0.99	$ 0.94	$ 0.85	$ 0.81	$ 0.84	$ 0.55	$ 0.73	$ 0.74	$ 3.60	$ 2.86	$ 2.61
Weighted average common shares outstanding (in shares)									15,730,016	14,768,687	13,325,128
Weighted average common shares issuable upon exercise of stock options and under the employee stock purchase plan (in shares)									237,759	296,043	355,344
Weighted average common and common equivalent shares outstanding (in shares)									15,967,775	15,064,730	13,680,472