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				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic:
Net income (loss)	$ (320)	$ 17,625	$ (9,911)	$ (16,008)	$ 17,305	$ (25,919)
Basic (in shares)	20,856		20,720		20,879	20,703
Basic (in dollars per share)	$ (0.02)		$ (0.48)		$ 0.83	$ (1.25)
Diluted:
Net income (loss)	$ (320)	$ 17,625	$ (9,911)	$ (16,008)	$ 17,305	$ (25,919)
Basic (in shares)	20,856		20,720		20,879	20,703
Unvested restricted stock and DSU's (in shares)	0		0		0	0
Employee stock options (in shares)	0		0		0	0
Diluted (in shares)	20,856		20,720		20,879	20,703
Diluted (in dollars per share)	$ (0.02)		$ (0.48)		$ 0.83	$ (1.25)