Note 12 - Stock-based Compensation - Stock Plan Activities (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Options outstanding, stock option awards exercised (in shares)	(3,299)
Incentive Plan [Member]
Awards available, beginning balance (in shares)	4,592	968	805
Options outstanding, beginning balance (in shares)	24,885	21,050	17,491
Weighted average exercise price, beginning balance (in dollars per share)			$ 6.49
Awards available, plan amendment (in shares)	7,500	8,000	4,000
Awards available, Restricted stock awards granted (in shares)	(1,936)	(31)	(27)
Awards available, stock option awards granted (in shares)	(6,753)	(7,469)	(4,511)
Options outstanding, stock option awards granted (in shares)	6,753	7,469	4,511
Weighted average exercise price, stock option awards granted (in dollars per share)		$ 8.06	$ 3.91
Options outstanding, stock option awards exercised (in shares)	(2,705)	(510)	(251)
Weighted average exercise price, stock option awards exercised (in dollars per share)	$ 4.36	$ 3.56	$ 3.75
Awards available, stock option awards cancelled (in shares)	248	3,124	701
Options outstanding, stock option awards cancelled (in shares)	(248)	(3,124)	(701)
Weighted average exercise price, stock option awards cancelled (in dollars per share)	$ 7.62	$ 6.93	$ 6.82
Awards available, ending balance (in shares)	3,651	4,592	968
Options outstanding, ending balance (in shares)	28,685	24,885	21,050
Weighted average exercise price, ending balance (in dollars per share)	$ 7.90	$ 6.52	$ 5.96
Inducement Plan [Member]
Awards available, beginning balance (in shares)	229
Options outstanding, beginning balance (in shares)	4,171
Weighted average exercise price, beginning balance (in dollars per share)	$ 3.88
Awards available, plan amendment (in shares)	1,500
Awards available, stock option awards granted (in shares)	(1,003)
Options outstanding, stock option awards granted (in shares)	1,003
Weighted average exercise price, stock option awards granted (in dollars per share)	$ 13.91
Options outstanding, stock option awards exercised (in shares)	(592)
Weighted average exercise price, stock option awards exercised (in dollars per share)	$ 3.63
Awards available, stock option awards cancelled (in shares)	174
Options outstanding, stock option awards cancelled (in shares)	(174)
Weighted average exercise price, stock option awards cancelled (in dollars per share)	$ 3.67
Awards available, ending balance (in shares)	900	229
Options outstanding, ending balance (in shares)	4,408	4,171
Weighted average exercise price, ending balance (in dollars per share)	$ 6.20	$ 3.88