Note 11 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-based compensation	$ 4,206	$ 674	$ 5,823	$ 1,347
Share-based Payment Arrangement, Option [Member]
Stock-based compensation		0		0
Equity Classified Awards [Member]
Stock-based compensation	1,880	642	3,300	1,475
Liability Classified Awards [Member]
Stock-based compensation	2,326	32	2,523	(128)
Research and Development Expense [Member] | Share-based Payment Arrangement, Option [Member]
Stock-based compensation	188	0	188	0
Research and Development Expense [Member] | Restricted Stock [Member]
Stock-based compensation	273	142	519	353
Research and Development Expense [Member] | Stock Appreciation Rights (SARs) [Member]
Stock-based compensation	(40)	16	149	(61)
Selling, General and Administrative Expenses [Member] | Share-based Payment Arrangement, Option [Member]
Stock-based compensation	598	0	598	0
Selling, General and Administrative Expenses [Member] | Restricted Stock [Member]
Stock-based compensation	821	500	1,995	1,122
Selling, General and Administrative Expenses [Member] | Stock Appreciation Rights (SARs) [Member]
Stock-based compensation	$ (2)	$ 16	$ 6	$ (67)