Note 10 - Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Benefit at statutory rate	$ (15,228)	$ (21,832)	$ (32,562)
State income taxes	(587)	594	(585)
Research and development credits	(16,933)	(13,283)	(12,983)
Change in valuation allowance	31,917	13,757	40,028
Impact of foreign operations	(1,045)	5,925	(1,951)
Unrecognized tax benefits	6,725	5,340	3,596
Stock-based compensation	(4,731)	(381)	(10,248)
Prior year return to provision adjustment	(1,167)	1,422	1,105
Section 162(m)	1,046	0	0
Effect of U. S. tax law change	0	0	(4,602)
Impairment of intangibles	0	0	(2,328)
Other	399	247	(646)
Total	$ 396	$ (8,211)	$ (21,176)