Note 12 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Tax credits	$ 26,302	$ 23,501
Stock-based compensation	2,027	2,392
Deferred compensation	8,526	7,895
Net operating losses	5,818	1,150
Other expenses not currently deductible	5,151	4,617
Deferred tax assets, gross	47,824	39,555
Valuation allowance	(19,520)	(18,190)
Deferred tax assets, net of valuation allowance	28,304	21,365
Depreciation and amortization	(5,067)	(1,600)
Undistributed foreign earnings	(375)	(77)
Other expenses currently deductible	(945)	(1,132)
Deferred tax liabilities	(6,387)	(2,809)
Net deferred tax assets	$ 21,917	$ 18,556