Note 7 - Earnings per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings per Share
Net income	$ 15,242	$ 23,624	$ 22,349	$ 17,982	$ 38,866	$ 40,331
Basic EPS	$ 0.88		$ 1.41		$ 2.36	$ 2.55
Diluted EPS	$ 0.87		$ 1.39		$ 2.33	$ 2.52
Weighted average common shares outstanding	17,345,324		15,813,932		16,485,218	15,808,788
Weighted average common shares issuable upon exercise of stock options and under the employee stock purchase plan (in shares)	203,783		231,307		215,464	226,606
Weighted average common and common equivalent shares outstanding (in shares)	17,549,107		16,045,239		16,700,682	16,035,394