Note 14 - Net Income Per Share - Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Net income	$ 14,533	$ 13,368	$ 13,232	$ 17,234	$ 16,543	$ 15,641	$ 41,133	$ 49,418
Weighted average shares outstanding - basic (in shares)	22,582			22,550			22,553	22,633
Dilutive securities (in shares)	220			260			206	268
Weighted average shares outstanding- diluted (in shares)	22,802			22,810			22,759	22,901
Net income per share, basic (in dollars per share)	$ 0.64			$ 0.76			$ 1.82	$ 2.18
Net income per share, diluted (in dollars per share)	$ 0.64			$ 0.76			$ 1.81	$ 2.16