Note 6 - Defined Benefit Plan (Details Textual)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	May 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Apr. 01, 2020 USD ($)	Jul. 01, 2019 USD ($)
Pension Plan [Member] | Pentegra Defined Benefit Plan [Member]
Pension Cost (Reversal of Cost)		$ 83,000	$ 20,000	$ 142,000	$ 41,000
Multiplayer Plan, Contributions by Employer				$ 0		$ 225,000
Multiemployer Plan, Contributions by Employer, Percentage						5.00%
Multiemployer Plan, Unfunded Pension Liability								$ 572,000
Multiemployer Plan, Funded Percentage								87.00%
Postemployment Retirement Benefits [Member] | Bank DB Plan [Member]
Defined Benefit Plan, Number of Current and Former Employees		50		50
Defined Benefit Plan, Plan Assets, Amount, Ending Balance		$ 3,744,342		$ 3,744,342			$ 2,392,111
Defined Benefit Plan, Benefit Obligation, Ending Balance							3,951,473
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 1,387,186
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax		$ 1,542,112		$ 1,542,112			$ 1,559,362
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		3.50%		3.50%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase		0.00%		0.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate		3.50%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets		3.50%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase		0.00%