Note 6 - Federal Income Taxes (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Effective Income Tax Rate Reconciliation, Percent, Total	22.20%	27.90%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 114,000	$ 223,000
Unrecognized Tax Benefits, Ending Balance	$ 0
State and Local Jurisdiction [Member]
Open Tax Year	2014