Note 10 - Income Taxes - Components of Company's Net Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Net operating loss carry forwards	$ 48,481	$ 39,888
Research and development credits	84,268	69,320
Stock-based compensation	8,884	9,055
Accrued expenses and allowances	1,897	2,334
Amortization and depreciation	0	1,408
Operating lease liability	7,345	0
Other temporary differences	6,884	6,411
Foreign tax credit	2,338	2,338
Valuation allowance	(123,989)	(92,315)
Total deferred tax assets	36,108	38,439
Deferred tax liabilities
Acquired intangible assets	(16,092)	(22,593)
Convertible debt	(6,444)	(11,596)
Amortization and depreciation	(2,123)	0
Right of use asset	(6,806)	0
Other deferred tax liabilities	(1,482)	(603)
Total deferred tax liabilities	(32,947)	(34,792)
Deferred tax assets, net	$ 3,161	$ 3,647