Note 7 - Income Taxes - Income Tax Reconciliation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Expected federal income taxes	$ 8,708,000	$ 8,509,000	$ 7,285,000
Foreign tax rate differential	6,000	26,000	146,000
State income taxes, net of federal benefit and state tax credits	607,000	1,344,000	376,000
Share-based compensation	(5,713,000)	(1,579,000)	(3,041,000)
Compensation limit for covered employees	463,000
Federal tax credits	(261,000)	(419,000)	(150,000)
Uncertain tax positions	157,000	34,000	90,000
Nondeductible expenses (income) related to recapitalization		(24,000)	151,000
Goodwill Impairment	184,000
Tax depreciation method change			(308,000)
Withholding tax on repatriation of foreign earnings	18,000	107,000
GILTI	10,000	13,000	40,000
Other	28,000	102,000	73,000
Income Tax Expense (Benefit), Total	$ 4,207,000	$ 8,113,000	$ 4,662,000