Note 10 - Income Tax - Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Computed “expected” tax rate	21.00%	21.00%	34.00%
State taxes, net of federal tax benefit	1.80%	2.80%	3.50%
Meals and entertainment	0.20%	0.20%	0.30%
Tax credits	(6.20%)	(1.90%)	(0.60%)
Domestic production deduction			(2.60%)
Non-deductible ISO stock option expense		0.10%	0.10%
Unrecognized tax benefits	(0.70%)
Excess tax benefits on equity awards	(0.70%)	(1.30%)	(1.40%)
Excess compensation	0.60%	0.80%
Impact on deferred taxes of new legislation			(11.10%)
Other	0.40%	0.50%	0.10%
Change in valuation allowance	0.10%
Effective tax rate	16.50%	22.20%	22.30%