Note 11 - Income Taxes (Details Textual) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Percent, Total	92.80%		72.70%	2.80%	45.00%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				21.00%			35.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability		$ (44.4)		$ (27.5)
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent						21.00%
Foreign Tax Authority [Member] | Kenya Revenue Authority [Member]
National Corporate Tax Rate				37.50%
Foreign Tax Authority [Member] | Israel Tax Authority [Member]
National Corporate Tax Rate				16.00%