Note 7 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		35.00%
Provisional Tax Expense (Benefit) for Tax Cuts and Jobs Act		$ (1,900,000)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Depreciation, Amount		0
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount		535,000
Effective Income Tax Rate Reconcilation, Withholding Tax on Repatriation of Foreign Earnings		706,000
Unrecognized Tax Benefits		843,000	662,000	$ 589,000
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		5,000	2,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		$ 620,000	$ 472,000
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%