Note 9 - Earnings Per Share - Summary of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net income	$ 19,642	$ 6,391
Basic (in shares)	85,853	83,933
Plus: net effect of dilutive stock options and restricted stock units (in shares)	2,761	1,749
Weighted average common shares outstanding-diluted (in shares)	88,614	85,682
Net income per common share -- basic (in dollars per share)	$ 0.23	$ 0.08
Net income per common share -- diluted (in dollars per share)	$ 0.22	$ 0.07