Note 6 - (Loss) Income Per Common Share - Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income (loss)	$ (979)	$ 2,748	$ 21,451	$ 15,280	$ (12,017)	$ (15,824)	$ 24,199	$ (27,842)	$ 23,220	$ (12,562)	$ (9,457)	$ (94,909)	$ (26,751)
Series B Preferred Stock dividends declared	(138)			(138)					(414)	(414)
Net (loss) income applicable to common shares	$ (1,117)	$ 2,610	$ 21,313	$ 15,142	$ (12,155)	$ (15,962)	$ 23,923	$ (28,118)	$ 22,806	$ (12,976)	$ (10,009)	$ (95,461)	$ (27,303)
Weighted average number of common shares outstanding - basic (in shares)	536,966			529,838					535,542	526,098
Dilutive restricted stock units, warrants and deferred shares (in shares)	0			5,950					6,227	0
Diluted weighted average common shares (in shares)	536,966			535,788					541,769	526,098
Basic (loss) income per common share after preferred dividends (in cents) (in dollars per share)	$ (0.002)	$ 0.005	$ 0.04	$ 0.029	$ (0.023)	$ (0.030)	$ 0.043	$ (0.054)	$ 0.043	$ (0.025)	$ (0.019)	$ (0.195)	$ (0.063)
Diluted (loss) income per common share after preferred dividends (in cents) (in dollars per share)	$ (0.002)	$ 0.005	$ 0.04	$ 0.028	$ (0.023)	$ (0.030)	$ 0.043	$ (0.054)	$ 0.042	$ (0.025)	$ (0.019)	$ (0.195)	$ (0.063)