Note 9 - Income Taxes (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2019
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%
Elimination of AMT Operating Loss Carryforwards	$ 91.3
Income Tax Expense (Benefit), Total	$ (5.0)
Percentage of AMT Credit Carryforward to Be Received			50.00%
Amount of AMT Credit Carryforwards Expected to Be Received			$ 2.5