Note 11 - Income Taxes - Components of Company's Net Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets
Net operating loss carry forwards	$ 39,888	$ 34,366
Research and development credits	69,320	62,118
Stock-based compensation	9,055	6,021
Accrued expenses and allowances	2,334	2,004
Amortization and depreciation	1,408	4,910
Other temporary differences	6,411	4,018
Foreign tax credit	2,338	2,557
Valuation allowance	(92,315)	(78,538)
Total deferred tax assets	38,439	37,456
Deferred tax liabilities
Acquired intangible assets	(22,593)	(26,602)
Acquired tangible assets		(255)
Convertible debt	(11,596)	(15,213)
Other deferred tax liabilities	(603)	(68)
Total deferred tax liabilities	(34,792)	(42,138)
Deferred tax assets, net	$ 3,647
Deferred tax liabilities, net		$ (4,682)