Note 3 - Income Taxes (Details Textual) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Percent, Total	18.50%	34.70%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				35.00%
Increase (Decrease) in Income Tax Expense from Exercise of Options and Dividends Paid to Non-vested Shareholders	$ (350,000)
Increase (Decrease) in Income Tax Expense from Non-deductible Recapitalization Expenses	$ 67,000
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%