Note 5 - Loans Receivable and Allowance for Loan Losses - Activity in Allowance for Loan Losses (Details) - USD ($)		3 Months Ended			6 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017	Mar. 31, 2018
Beginning balance		$ 2,836,987		$ 2,357,528	$ 2,821,903		$ 2,194,815
Charge-offs		(83,253)		(20,437)	(130,665)		(24,515)
Recoveries		34,699		13,900	37,195		20,691
Provision for credit losses		242,496		120,000	302,496		280,000
Ending balance		3,030,929		2,470,991	3,030,929		2,470,991
Loans		374,648,865			374,648,865			$ 389,221,239
Financial Asset Originated [Member]
Individually evaluated for impairment, allowance		259,723		270,329	259,723		270,329
Collectively evaluated for impairment, allowance		2,301,290		2,200,662	2,301,290		2,200,662
Individually evaluated for impairment		6,805,310		7,122,736	6,805,310		7,122,736
Collectively evaluated for impairment		263,303,658		242,235,707	263,303,658		242,235,707
Loans		270,108,968	[1]	249,358,443	270,108,968	[1]	249,358,443	277,250,109	[1]
Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		469,916			469,916
Individually evaluated for impairment		1,756,614		1,737,062	1,756,614		1,737,062
Collectively evaluated for impairment		102,783,283		116,553,794	102,783,283		116,553,794
Loans		104,539,897		118,290,856	104,539,897		118,290,856	111,971,130
Real Estate Loans [Member]
Loans		299,698,738			299,698,738			309,465,974
Real Estate Loans [Member] | Financial Asset Originated [Member]
Loans	[1]	202,817,744			202,817,744			206,141,595
Real Estate Loans [Member] | Financial Asset Acquired [Member]
Loans		96,880,994			96,880,994			103,324,379
Real Estate Loans [Member] | Residential [Member]
Beginning balance		601,211		544,557	608,723		553,539
Charge-offs		(5,722)		(8,907)	(13,769)		(8,907)
Recoveries		1,475			2,242
Provision for credit losses		68,712		(7,362)	68,480		(16,344)
Ending balance		665,676		528,288	665,676		528,288
Real Estate Loans [Member] | Residential [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance		257,866		270,329	257,866		270,329
Collectively evaluated for impairment, allowance		260,437		257,959	260,437		257,959
Individually evaluated for impairment		1,710,906		1,684,871	1,710,906		1,684,871
Collectively evaluated for impairment		85,018,504		73,121,605	85,018,504		73,121,605
Loans		86,729,410		74,806,476	86,729,410		74,806,476
Real Estate Loans [Member] | Residential [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		147,373			147,373
Individually evaluated for impairment		1,002,307		1,260,264	1,002,307		1,260,264
Collectively evaluated for impairment		67,930,546		76,403,162	67,930,546		76,403,162
Loans		68,932,853		77,663,426	68,932,853		77,663,426
Real Estate Loans [Member] | Investor Loans [Member]
Beginning balance		63,506		64,471	51,690		35,275
Charge-offs		(2,531)		(11,044)	(8,111)		(15,122)
Recoveries				12,822	64		18,129
Provision for credit losses		253,596		(13,994)	270,928		13,973
Ending balance		314,571		52,255	314,571		52,255
Real Estate Loans [Member] | Investor Loans [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance		1,857			1,857
Collectively evaluated for impairment, allowance		50,278		52,255	50,278		52,255
Individually evaluated for impairment		59,426		5,294	59,426		5,294
Collectively evaluated for impairment		7,820,735		9,622,035	7,820,735		9,622,035
Loans		7,880,161		9,627,329	7,880,161		9,627,329
Real Estate Loans [Member] | Investor Loans [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		262,436			262,436
Individually evaluated for impairment		499,838		210,988	499,838		210,988
Collectively evaluated for impairment		16,502,829		18,212,904	16,502,829		18,212,904
Loans		17,002,667		18,423,892	17,002,667		18,423,892
Real Estate Loans [Member] | Commercial [Member]
Beginning balance		1,355,886		1,312,158	1,253,383		1,375,894
Charge-offs					(31,320)
Recoveries		31,320			31,320
Provision for credit losses		(74,765)		48,275	59,058		(15,461)
Ending balance		1,312,441		1,360,433	1,312,441		1,360,433
Loans		115,696,478			115,696,478			112,166,254
Real Estate Loans [Member] | Commercial [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		1,272,762		1,360,433	1,272,762		1,360,433
Individually evaluated for impairment		4,251,209		4,707,655	4,251,209		4,707,655
Collectively evaluated for impairment		101,427,804		90,250,315	101,427,804		90,250,315
Loans		105,679,013	[1]	94,957,970	105,679,013	[1]	94,957,970	100,403,769	[1]
Real Estate Loans [Member] | Commercial [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		39,679			39,679
Individually evaluated for impairment		196,697		201,573	196,697		201,573
Collectively evaluated for impairment		9,820,768		11,912,984	9,820,768		11,912,984
Loans		10,017,465		12,114,557	10,017,465		12,114,557	11,762,485
Real Estate Loans [Member] | Commercial Construction [Member]
Beginning balance		14,793		26,987	33,430		9,031
Charge-offs
Recoveries
Provision for credit losses		(2,403)		(14,913)	(21,040)		3,043
Ending balance		12,390		12,074	12,390		12,074
Loans		3,457,168			3,457,168			7,115,803
Real Estate Loans [Member] | Commercial Construction [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		11,381		12,074	11,381		12,074
Individually evaluated for impairment
Collectively evaluated for impairment		2,529,160		2,081,647	2,529,160		2,081,647
Loans		2,529,160	[1]	2,081,647	2,529,160	[1]	2,081,647	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		1,009			1,009
Individually evaluated for impairment
Collectively evaluated for impairment		928,008		1,058,534	928,008		1,058,534
Loans		928,008		1,058,534	928,008		1,058,534	1,352,019
Commercial Portfolio Segment [Member]
Beginning balance		609,372		343,094	673,982		149,461
Charge-offs		(75,000)			(75,000)
Recoveries				206			381
Provision for credit losses		(1,761)		(16,170)	(66,371)		177,288
Ending balance		532,611		327,130	532,611		327,130
Loans	[2]	37,889,576			37,889,576			40,143,965
Commercial Portfolio Segment [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		528,363		327,130	528,363		327,130
Individually evaluated for impairment		769,307		702,352	769,307		702,352
Collectively evaluated for impairment		35,365,069		33,340,191	35,365,069		33,340,191
Loans		36,134,376	[1],[2]	34,042,543	36,134,376	[1],[2]	34,042,543	38,302,739	[1],[2]
Commercial Portfolio Segment [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		4,248			4,248
Individually evaluated for impairment
Collectively evaluated for impairment		1,755,200		1,668,783	1,755,200		1,668,783
Loans		1,755,200	[2]	1,668,783	1,755,200	[2]	1,668,783	1,841,226	[2]
Home Equity Loans [Member]
Beginning balance		68,267		64,661	69,459		70,071
Charge-offs
Recoveries
Provision for credit losses		4,564		(2,091)	3,372		(7,501)
Ending balance		72,831		62,570	72,831		62,570
Loans		19,367,708			19,367,708			19,995,789
Home Equity Loans [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		57,845		62,570	57,845		62,570
Individually evaluated for impairment		7,254		22,564	7,254		22,564
Collectively evaluated for impairment		14,176,278		13,641,850	14,176,278		13,641,850
Loans		14,183,532	[1]	13,664,414	14,183,532	[1]	13,664,414	13,956,327	[1]
Home Equity Loans [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		14,986			14,986
Individually evaluated for impairment
Collectively evaluated for impairment		5,184,176		6,459,424	5,184,176		6,459,424
Loans		5,184,176		6,459,424	5,184,176		6,459,424	6,039,462
Consumer Portfolio Segment [Member]
Beginning balance		123,952		1,600	131,236		1,544
Charge-offs				(486)	(2,465)		(486)
Recoveries		1,904		872	3,569		2,181
Provision for credit losses		(27,180)		126,255	(33,664)		125,002
Ending balance		98,676		128,241	98,676		128,241
Loans	[3]	17,692,843			17,692,843			19,615,511
Consumer Portfolio Segment [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		98,491		128,241	98,491		128,241
Individually evaluated for impairment		7,208			7,208
Collectively evaluated for impairment		16,966,108		20,178,064	16,966,108		20,178,064
Loans		16,973,316	[1],[3]	20,178,064	16,973,316	[1],[3]	20,178,064	18,849,448	[1],[3]
Consumer Portfolio Segment [Member] | Financial Asset Acquired [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		185			185
Individually evaluated for impairment		57,772		64,237	57,772		64,237
Collectively evaluated for impairment		661,756		838,003	661,756		838,003
Loans		719,528		902,240	719,528		902,240	$ 766,063	[3]
Unallocated Financing Receivables [Member]
Beginning balance
Charge-offs
Recoveries
Provision for credit losses		21,733			21,733
Ending balance		21,733			21,733
Unallocated Financing Receivables [Member] | Financial Asset Originated [Member]
Individually evaluated for impairment, allowance
Collectively evaluated for impairment, allowance		21,733			21,733
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.