Note 12 - Fair Value Measurements - Reconciliation of Foreclosed Real Estate, Measured On Nonrecurring Basis Using Significant Unobservable Inputs (Details) - USD ($)	9 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018
Transfer to foreclosed real estate	$ 145,820	$ 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	(145,820)		(35,896)
Loss on sale of foreclosed real estate	(4,232)		(1,299)
Balance at end of period	$ 457,778		$ 457,778