Note 12 - Stock-Based Compensation - Stock Plan Activities (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Options Outstanding
Options outstanding, stock option awards exercised (in shares)	(3,044,000)
Incentive Plan
Awards Available
Awards available, beginning balance (in shares)	3,651,000	4,592,000	968,000
Awards available number of additional shares authorized (in shares)	8,000,000	7,500,000	8,000,000
Awards available, Restricted stock awards granted (in shares)	(2,948,000)	(1,936,000)	(31,000)
Awards available, stock option awards cancelled (in shares)	254,000
Awards available, stock option awards granted (in shares)	(5,784,000)	(6,753,000)	(7,469,000)
Awards available, stock option awards cancelled (in shares)	1,033,000	248,000	3,124,000
Awards available, ending balance (in shares)	4,206,000	3,651,000	4,592,000
Options Outstanding
Options outstanding, beginning balance (in shares)	28,685,000	24,885,000	21,050,000
Options outstanding, stock awards granted	5,784,000	6,753,000	7,469,000
Options outstanding, stock option awards exercised (in shares)	(2,257,000)	(2,705,000)	(510,000)
Options outstanding, stock option awards cancelled (in shares)	(1,033,000)	(248,000)	(3,124,000)
Options outstanding, ending balance (in shares)	31,179,000	28,685,000	24,885,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price [Abstract]
Weighted average exercise price, beginning balance (in dollars per share)			$ 5.96
Weighted average exercise price, stock option awards granted (in dollars per share)	$ 10.70	$ 11.57	8.06
Weighted average exercise price, stock option awards exercised (in dollars per share)	5.00	4.36	3.56
Weighted average exercise price, stock option awards cancelled (in dollars per share)	10.02	7.62	6.93
Weighted average exercise price, ending balance (in dollars per share)	$ 8.56	$ 7.90	$ 6.52
Inducement Plan
Awards Available
Awards available, beginning balance (in shares)	900,000	229,000	171,000
Awards available number of additional shares authorized (in shares)	1,926,000	1,500,000	2,900,000
Awards available, Restricted stock awards granted (in shares)	(603,000)	(1,003,000)	(3,002,000)
Awards available, stock option awards cancelled (in shares)	15,000	174,000	160,000
Awards available, stock option awards granted (in shares)	(1,819,000)
Awards available, stock option awards cancelled (in shares)	528,000
Awards available, ending balance (in shares)	947,000	900,000	229,000
Options Outstanding
Options outstanding, beginning balance (in shares)	4,408,000	4,171,000	1,329,000
Options outstanding, stock awards granted	1,819,000	1,003,000	3,002,000
Options outstanding, stock option awards exercised (in shares)	(358,000)	(592,000)	0
Options outstanding, stock option awards cancelled (in shares)	(528,000)	(174,000)	(160,000)
Options outstanding, ending balance (in shares)	5,341,000	4,408,000	4,171,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price [Abstract]
Weighted average exercise price, beginning balance (in dollars per share)	$ 6.20	$ 3.88	$ 3.60
Weighted average exercise price, stock option awards granted (in dollars per share)	13.54	13.91	4.02
Weighted average exercise price, stock option awards exercised (in dollars per share)	3.45	3.63
Weighted average exercise price, stock option awards cancelled (in dollars per share)	7.44	3.67	4.15
Weighted average exercise price, ending balance (in dollars per share)	$ 8.80	$ 6.20	$ 3.88