Note 2 - Basis of Presentation and Summary of Significant Accounting Policies (Details Textual) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017 USD ($)	Sep. 30, 2019	Sep. 30, 2018 USD ($)
Number of Reportable Segments	1
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				24.30%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability		$ (4.3)		$ (4.3)
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%