Note 9 - Earnings Per Share - Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
EARNINGS PER SHARE
Net income	$ 10,613	$ 10,204	$ 17,496	$ 15,470
Weighted average shares used to compute basic EPS (in shares)	40,869	40,082	40,737	39,994
Dilutive effect of share-based awards (in shares)	96	258	73	248
Weighted average shares used to compute diluted EPS (in shares)	40,965	40,340	40,810	40,242
Basic (in dollars per share)	$ 0.26	$ 0.25	$ 0.43	$ 0.39
Diluted (in dollars per share)	$ 0.26	$ 0.25	$ 0.43	$ 0.38