Note 14 - Income Taxes (Details Textual) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2019
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	23.00%	28.90%	34.00%	23.00%	28.90%
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent						21.00%
Lighting Reporting Unit [Member]
Deferred Tax Assets, Increase During Period, Impairment of Goodwill	$ 4.8		$ 10.7