Note 5 - Loans Receivable and Allowance for Loan Losses - Number of Contracts and Outstanding Loan Balance at Time of Modification (Details)	3 Months Ended		9 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Financing Receivable, Modifications, Number of Contracts	0
Real Estate Loans [Member] | Residential [Member]
Financing Receivable, Modifications, Number of Contracts		2
Outstanding recorded investment		$ 50,432
Real Estate Loans [Member] | One to four family, Residential [Member]
Financing Receivable, Modifications, Number of Contracts			1	3
Outstanding recorded investment			$ 20,565	$ 52,363