Note 6 - Income Taxes (Details Textual) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ 713,826		$ 713,826	[1]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		317,531
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration		312,272
Income Tax Examination, Penalties and Interest Expense, Total		0	0
Unrecognized Tax Benefits, Ending Balance		0	$ 0
State and Local Jurisdiction [Member] | Wisconsin Department of Revenue [Member]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		$ 6,500,000

[1] As adjusted for the retrospective adoption of ASC 606