Note 12 - Fair Value Measurements - Reconciliation of Foreclosed Real Estate, Measured On Nonrecurring Basis Using Significant Unobservable Inputs (Details) - USD ($)	6 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Transfer to foreclosed real estate	$ 130,200	$ 17,305
Fair Value, Inputs, Level 3 [Member]
Balance at beginning of period	457,778	$ 503,094	$ 503,094
Transfer to foreclosed real estate	150,052		23,834
Write-down of foreclosed real estate			(31,955)
Proceeds from sale of foreclosed real estate	(19,641)		(35,896)
Loss on sale of foreclosed real estate	(211)		(1,299)
Balance at end of period	$ 587,978		$ 457,778