Note 1 - Nature of Operations and Summary of Significant Accounting Policies (Details Textual)				12 Months Ended
	Oct. 12, 2015 USD ($) $ / shares	Sep. 11, 2015 USD ($) $ / shares	Oct. 10, 2012 USD ($) $ / shares shares	Mar. 31, 2016 USD ($) $ / shares shares	Mar. 31, 2015 USD ($) shares	Dec. 31, 2015	Apr. 15, 2015 $ / shares	Oct. 31, 2012 shares
Core Deposits [Member]
Finite-Lived Intangible Asset, Useful Life				8 years
Fraternity Community Bancorp, Inc. [Member]
Business Acquisition, Share Price | $ / shares	$ 19.25
Payments to Acquire Businesses, Gross	$ 25,700,000
Fairmount Bancorp, Inc. [Member]
Business Acquisition, Share Price | $ / shares		$ 30					$ 30
Business Combination, Consideration Transferred		$ 15,400,000
Payments to Acquire Businesses, Gross		$ 14,200,000
Fraternity Community Bancorp, Inc. [Member]
Assets				$ 160,900,000
Common Stock, Shares, Issued | shares			3,703,000	3,413,646	3,417,713
Share Price | $ / shares			$ 10
Proceeds from Issuance of Common Stock			$ 35,580,000
Noninterest Expense Offering Cost			$ 1,450,000
Employee Stock Option Plan, Subscribed Percentage			8.00%
Employee Stock Ownership Plan (ESOP), Number of Allocated Shares | shares			296,240	59,248	44,436			296,240
Number of Branches						5
Investment in Federal Home Loan Bank Stock Par Value Per Share | $ / shares				$ 100
Federal Home Loan Bank Stock				$ 1,042,500	$ 522,700
Assets				392,916,555	$ 291,039,769
Payments to Acquire Businesses, Gross				$ 14,192,370