Note 12 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Tax credits	$ 18,080	$ 11,833
Stock-based compensation	6,237	10,040
Deferred compensation	7,110	6,829
Net operating losses	615	1,133
Other expenses not currently deductible	2,323	1,852
Deferred tax assets, gross	34,365	31,687
Valuation allowance	(15,411)	(13,041)
Deferred tax assets, net of valuation allowance	18,954	18,646
Depreciation and amortization	(1,259)	(711)
Undistributed foreign earnings	(77)	(1,105)
Other expenses currently deductible	(425)	0
Deferred tax liabilities	(1,761)	(1,816)
Net deferred tax assets	$ 17,193	$ 16,830