Note 4 - Investment Securities Available for Sale (Details Textual) - USD ($)	3 Months Ended	6 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Proceeds from Sale of Debt Securities, Available-for-sale	$ 0	$ 4,243,760	$ 0	$ 4,243,760
Gain on Sale of Investments		$ 23,352
Loss on Sale of Investments				$ 12,971
Debt Securities, Available-for-sale, Amortized Cost, Total	72,331,577		72,331,577		$ 78,267,079
Debt Securities, Available-for-sale, Total	68,862,989		68,862,989		75,404,136
Pledged Financial Instruments, Not Separately Reported, Securities, Total	744,186		744,186		744,186
Collateral Pledged [Member]
Debt Securities, Available-for-sale, Restricted	713,599		713,599		$ 723,023
Fraternity Community Bancorp, Inc. [Member] \| Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-sale, Amortized Cost, Total	38,258		38,258
Debt Securities, Available-for-sale, Total	$ 38,858		$ 38,858

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of restricted investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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The difference between the carrying value and the sale price of an investment. A gain would be recognized when the sale price of the investment is greater than the carrying value of the investment. This element refers to the Gain included in earnings and not to the cash proceeds of the sale.

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The difference between the carrying value and the sale price of an investment. A loss would be recognized when the sale price of the investment is less than the carrying value of the investment. This element refers to the Loss included in earnings and not to the cash proceeds of the sale.

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Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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