Note 14 - Income Taxes (Details Textual) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Deferred Tax Assets, Valuation Allowance, Total			$ 5,790,102	$ 42,364
Loss Carryforwards, Charitable Contribution			102,742
Unrecognized Tax Benefits, Ending Balance			0
Unrecognized Tax Benefits, Period Increase (Decrease), Total			0
Loss Carryforwards, AMT Credit Carryovers			$ 245,620
Charitable Contribution Carryforwards, Limited Life			5 years
AMT Credit Carryovers, Limited Life			5 years
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 2,300,000
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total			$ 12,000,000
Domestic Tax Authority [Member] | Fraternity Community Bancorp, Inc. [Member]
Operating Loss Carryforwards, Total			4,900,000
Domestic Tax Authority [Member] | Fairmount Bancorp, Inc. [Member]
Operating Loss Carryforwards, Total			$ 1,900,000
Domestic Tax Authority [Member] | Earliest Tax Year [Member]
Operating Loss Carryforwards, Expiration Date			Mar. 31, 2030
Domestic Tax Authority [Member] | Latest Tax Year [Member]
Operating Loss Carryforwards, Expiration Date			Mar. 31, 2037
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total			$ 11,000,000
State and Local Jurisdiction [Member] | Earliest Tax Year [Member]
Operating Loss Carryforwards, Expiration Date			Mar. 31, 2030
State and Local Jurisdiction [Member] | Latest Tax Year [Member]
Operating Loss Carryforwards, Expiration Date			Mar. 31, 2037