Note 7 - Net Income (Loss) Per Share - Calculations of Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Basic:
Net income (loss)	$ 17,625	$ (16,008)
Basic (in shares)	20,902	20,686
Basic (in dollars per share)	$ 0.84	$ (0.77)
Diluted:
Net income (loss)	$ 17,625	$ (16,008)
Basic (in shares)	20,902	20,686
Unvested restricted stock and DSU's (in shares)	28	0
Employee stock options (in shares)	0	0
Diluted (in shares)	20,930	20,686
Diluted (in dollars per share)	$ 0.84	$ (0.77)