Note 7 - EARNINGS PER SHARE - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
EARNINGS PER SHARE
Net income	$ 27,785	$ 29,114	$ 26,726	$ 25,121	$ 28,425	$ 27,157	$ 83,625	$ 80,703
Basic EPS	$ 1.65			$ 1.50			$ 4.97	$ 4.82
Diluted EPS	$ 1.64			$ 1.49			$ 4.94	$ 4.79
Weighted average common shares outstanding	16,846,200			16,717,303			16,814,787	16,731,847
Weighted average common shares issuable upon exercise of stock options and under the employee stock purchase plan (in shares)	136,200			130,648			123,522	131,356
Weighted average common and common equivalent shares outstanding	16,982,400			16,847,951			16,938,309	16,863,203