Note 7 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2019	Jun. 30, 2018
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	27.55%		35.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 348
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ (95)
Effective Income Tax Rate Reconciliation, Percent	42.70%	16.70%	31.70%	19.70%
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent					21.00%	27.55%