Note 9 - Income Taxes (Details Textual)	6 Months Ended
	Jun. 30, 2018 USD ($)
Deferred Tax Assets, Gross, Total	$ 4,900,000
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	148,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	$ 0
Tax Year 2014 [Member]
Open Tax Year	2014
Tax Year 2015 [Member]
Open Tax Year	2015
Tax Year 2016 [Member]
Open Tax Year	2016
Tax Year 2017 [Member]
Open Tax Year	2017
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total	$ 13,300,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total	$ 16,000,000