Note 3 - Acquisitions (Details Textual)		3 Months Ended
	May 13, 2016 USD ($) $ / shares	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)
Core Deposits [Member]
Finite-Lived Intangible Asset, Useful Life	8 years	8 years
Fraternity Community Bancorp, Inc. [Member]
Business Acquisition, Share Price | $ / shares	$ 19.25
Payments to Acquire Businesses, Gross	$ 25,700,000		$ 25,704,871
Effective Income Tax Rate Reconciliation, Percent	39.45%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Tangible Assets, Net	$ 23,600,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	242,020
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition	108,872,041
Certain Loans Acquired in Transfer, Nonaccretable Difference	314,484
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition	108,557,557
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable FMV Adjustment	246,626
Fraternity Community Bancorp, Inc. [Member] | Performing Financial Instruments [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition	107,474,993
Certain Loans Acquired in Transfer, Nonaccretable Difference
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition	107,474,993
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable FMV Adjustment	301,672
Fraternity Community Bancorp, Inc. [Member] | Nonperforming Financial Instruments [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Contractually Required Payments Receivable at Acquisition	1,397,048
Certain Loans Acquired in Transfer, Nonaccretable Difference	314,484
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Expected to be Collected at Acquisition	1,082,564
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable FMV Adjustment	$ (55,046)
Financing Receivable, Impaired, Number of Contracts	23
Fraternity Community Bancorp, Inc. [Member] | Core Deposits [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 242,020