Note 13 - Income Taxes - Differences Between the Company's Effective Tax Rate and the Statutory Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income tax benefit at federal statutory rate (21% for 2022, 2021 and 2020)	$ (51,321)	$ (38,175)	$ (38,391)
State and local income taxes net of federal tax benefit	(1,816)	(2,288)	(2,544)
Permanent items	(1,608)	(1,343)	774
Rate change	0	0	(82)
Expiration of attribute carryforwards	0	(1,057)	3,774
Research and development tax credits	(9,793)	(5,994)	(4,080)
Foreign rate differential	1,862	1,940	542
Other	(5,485)	1,216	1,456
Change in valuation allowance	70,894	47,954	38,551
Income tax expense	$ 2,733	$ 2,253	$ 0