Note 5 - Loans Receivable and Allowance for Loan Losses - Activity in Allowance for Loan Losses (Details) - USD ($)		3 Months Ended			9 Months Ended
		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2018		Dec. 31, 2017	Mar. 31, 2018
Beginning balance		$ 3,030,929		$ 2,470,991	$ 2,821,903		$ 2,194,815
Charge-offs		(166,638)		(211,596)	(297,305)		(236,111)
Recoveries		86,815		5,142	124,012		25,833
Provision for credit losses		80,000		345,000	382,496		625,000
Ending balance		3,031,106		2,609,537	3,031,106		2,609,537
Loans		368,225,720			368,225,720			$ 389,221,239
Financial Asset Originated [Member]
Individually evaluated for impairment, allowance		253,811		272,707	253,811		272,707
Collectively evaluated for impairment, allowance		2,337,617		2,336,830	2,337,617		2,336,830
Individually evaluated for impairment		6,785,712		7,245,899	6,785,712		7,245,899
Collectively evaluated for impairment		261,081,550		265,078,879	261,081,550		265,078,879
Loans		267,867,262	[1]	272,324,778	267,867,262	[1]	272,324,778	277,250,109	[1]
Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		439,678			439,678
Individually evaluated for impairment		757,557		1,896,849	757,557		1,896,849
Collectively evaluated for impairment		99,600,901		113,619,050	99,600,901		113,619,050
Loans		100,358,458		115,515,899	100,358,458		115,515,899	111,971,130
Real Estate Loans [Member]
Loans		294,195,991			294,195,991			309,465,974
Real Estate Loans [Member] | Financial Asset Originated [Member]
Loans	[1]	201,184,464			201,184,464			206,141,595
Real Estate Loans [Member] | Financial Asset Acquired [Member]
Loans		93,011,527			93,011,527			103,324,379
Real Estate Loans [Member] | Residential [Member]
Beginning balance		665,676		528,288	608,723		553,539
Charge-offs					(13,769)		(8,907)
Recoveries		41,059		3,937	43,301		3,937
Provision for credit losses		(24,321)		35,875	44,159		19,531
Ending balance		682,414		568,100	682,414		568,100
Real Estate Loans [Member] | Residential [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance		253,811		272,707	253,811		272,707
Collectively evaluated for impairment, allowance		276,937		295,393	276,937		295,393
Individually evaluated for impairment		1,773,176		1,697,585	1,773,176		1,697,585
Collectively evaluated for impairment		84,774,908		85,532,435	84,774,908		85,532,435
Loans		86,548,084		87,230,020	86,548,084		87,230,020
Real Estate Loans [Member] | Residential [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		151,666			151,666
Individually evaluated for impairment		440,242		1,061,049	440,242		1,061,049
Collectively evaluated for impairment		65,815,018		73,640,662	65,815,018		73,640,662
Loans		66,255,260		74,701,711	66,255,260		74,701,711
Real Estate Loans [Member] | Investor Loans [Member]
Beginning balance		314,571		52,255	51,690		35,275
Charge-offs		(32,909)		(111,360)	(41,022)		(126,482)
Recoveries		33,609			33,675		18,129
Provision for credit losses		(36,632)		103,790	234,296		117,763
Ending balance		278,639		44,685	278,639		44,685
Real Estate Loans [Member] | Investor Loans [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		50,593		44,685	50,593		44,685
Individually evaluated for impairment		31,752		121,514	31,752		121,514
Collectively evaluated for impairment		7,305,529		7,254,483	7,305,529		7,254,483
Loans		7,337,281		7,375,997	7,337,281		7,375,997
Real Estate Loans [Member] | Investor Loans [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		228,046			228,046
Individually evaluated for impairment		261,659		579,172	261,659		579,172
Collectively evaluated for impairment		16,145,606		17,629,734	16,145,606		17,629,734
Loans		16,407,265		18,208,906	16,407,265		18,208,906
Real Estate Loans [Member] | Commercial [Member]
Beginning balance		1,312,441		1,360,433	1,253,383		1,375,894
Charge-offs				(100,236)	(31,320)		(100,236)
Recoveries					31,320
Provision for credit losses		(31,557)		148,707	27,501		133,246
Ending balance		1,280,884		1,408,904	1,280,884		1,408,904
Loans		115,045,570			115,045,570			112,166,254
Real Estate Loans [Member] | Commercial [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		1,241,051		1,408,904	1,241,051		1,408,904
Individually evaluated for impairment		4,139,177		4,500,043	4,139,177		4,500,043
Collectively evaluated for impairment		101,616,609		96,357,409	101,616,609		96,357,409
Loans		105,755,786	[1]	100,857,452	105,755,786	[1]	100,857,452	100,403,769	[1]
Real Estate Loans [Member] | Commercial [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		39,833			39,833
Individually evaluated for impairment				199,920			199,920
Collectively evaluated for impairment		9,289,784		11,960,924	9,289,784		11,960,924
Loans		9,289,784		12,160,844	9,289,784		12,160,844	11,762,485
Real Estate Loans [Member] | Commercial Construction [Member]
Beginning balance		12,390		12,074	33,430		9,031
Charge-offs
Recoveries
Provision for credit losses		(4,090)		11,100	(25,130)		14,143
Ending balance		8,300		23,174	8,300		23,174
Loans		2,602,530			2,602,530			7,115,803
Real Estate Loans [Member] | Commercial Construction [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		7,254		23,174	7,254		23,174
Individually evaluated for impairment
Collectively evaluated for impairment		1,543,313		3,995,441	1,543,313		3,995,441
Loans		1,543,313	[1]	3,995,441	1,543,313	[1]	3,995,441	5,763,784	[1]
Real Estate Loans [Member] | Commercial Construction [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		1,046			1,046
Individually evaluated for impairment
Collectively evaluated for impairment		1,059,217		856,970	1,059,217		856,970
Loans		1,059,217		856,970	1,059,217		856,970	1,352,019
Commercial Portfolio Segment [Member]
Beginning balance		532,611		327,130	673,982		149,461
Charge-offs		(133,729)			(208,729)
Recoveries		10,880		171	10,880		551
Provision for credit losses		160,895		45,987	94,524		223,276
Ending balance		570,657		373,288	570,657		373,288
Loans	[2]	36,983,002			36,983,002			40,143,965
Commercial Portfolio Segment [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		566,217		373,288	566,217		373,288
Individually evaluated for impairment		743,160		905,178	743,160		905,178
Collectively evaluated for impairment		34,533,333		38,083,051	34,533,333		38,083,051
Loans		35,276,493	[1],[2]	38,988,229	35,276,493	[1],[2]	38,988,229	38,302,739	[1],[2]
Commercial Portfolio Segment [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		4,440			4,440
Individually evaluated for impairment
Collectively evaluated for impairment		1,706,509		1,928,232	1,706,509		1,928,232
Loans		1,706,509	[2]	1,928,232	1,706,509	[2]	1,928,232	1,841,226	[2]
Home Equity Loans [Member]
Beginning balance		72,831		62,570	69,459		70,071
Charge-offs
Recoveries
Provision for credit losses		1,555		619	4,927		(6,882)
Ending balance		74,386		63,189	74,386		63,189
Loans		20,018,119			20,018,119			19,995,789
Home Equity Loans [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		59,952		63,189	59,952		63,189
Individually evaluated for impairment		6,785		21,579	6,785		21,579
Collectively evaluated for impairment		15,070,283		13,780,512	15,070,283		13,780,512
Loans		15,077,068	[1]	13,802,091	15,077,068	[1]	13,802,091	13,956,327	[1]
Home Equity Loans [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		14,434			14,434
Individually evaluated for impairment		164			164
Collectively evaluated for impairment		4,940,887		6,874,136	4,940,887		6,874,136
Loans		4,941,051		6,874,136	4,941,051		6,874,136	6,039,462
Consumer Portfolio Segment [Member]
Beginning balance		98,676		128,241	131,236		1,544
Charge-offs					(2,465)		(486)
Recoveries		1,267		1,034	4,836		3,216
Provision for credit losses		(4,214)		(1,078)	(37,878)		123,923
Ending balance		95,729		128,197	95,729		128,197
Loans	[3]	17,028,608			17,028,608			19,615,511
Consumer Portfolio Segment [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		95,516		128,197	95,516		128,197
Individually evaluated for impairment		91,662			91,662
Collectively evaluated for impairment		16,237,575		20,075,548	16,237,575		20,075,548
Loans		16,329,237	[1],[3]	20,075,548	16,329,237	[1],[3]	20,075,548	18,849,448	[1],[3]
Consumer Portfolio Segment [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		213			213
Individually evaluated for impairment		55,492		56,708	55,492		56,708
Collectively evaluated for impairment		643,880		728,392	643,880		728,392
Loans		699,372		785,100	699,372		785,100	$ 766,063	[3]
Unallocated Financing Receivables [Member]
Beginning balance		21,733
Charge-offs
Recoveries
Provision for credit losses		18,364			40,097
Ending balance		40,097			40,097
Unallocated Financing Receivables [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		40,097			40,097
Unallocated Financing Receivables [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance

[1] As a result of the acquisition of Fraternity Community Bancorp, Inc., the parent company of Fraternity Federal Savings and Loan, in May 2016 and Fairmount Bancorp, Inc., the parent company of Fairmount Bank, in September 2015, we have segmented the portfolio into two components, loans originated by Hamilton Bank "Legacy" and loans acquired from Fraternity Community Bancorp, Inc. and Fairmount Bancorp, Inc. "Acquired".

[2] "Legacy" commercial business loans at March 31, 2018 includes a $15.5 million pool of commercial lease loans purchased in June 2017 and $3.2 million in guaranteed SBA loans purchased in second half of fiscal 2018.

[3] "Legacy" consumer loans at March 31, 2018 includes $19.9 million of purchased loan pools consisting of recreational vehicles that were purchased in August and December 2017.