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						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic:
Net income (loss)	$ 18,333	$ (320)	$ 17,625	$ (4,343)	$ (9,911)	$ (16,008)	$ 35,638	$ (30,262)
Basic (in shares)	20,786			20,786			20,847	20,731
Basic (in dollars per share)	$ 0.88			$ (0.21)			$ 1.71	$ (1.46)
Diluted:
Net income (loss)	$ 18,333	$ (320)	$ 17,625	$ (4,343)	$ (9,911)	$ (16,008)	$ 35,638	$ (30,262)
Basic (in shares)	20,786			20,786			20,847	20,731
Unvested restricted stock and DSU's (in shares)	0			0			0	0
Employee stock options (in shares)	0			0			0	0
Diluted (in shares)	20,786			20,786			20,847	20,731
Diluted (in dollars per share)	$ 0.88			$ (0.21)			$ 1.71	$ (1.46)