Note 5 - Loans Receivable and Allowance for Loan Losses - Impaired Loans (Details) - USD ($)		3 Months Ended				6 Months Ended				12 Months Ended
		Sep. 30, 2018		Sep. 30, 2017		Sep. 30, 2018		Sep. 30, 2017		Mar. 31, 2018
Related allowance		$ 259,723		$ 270,329		$ 259,723		$ 270,329		$ 266,256	[1]
Unpaid contractual principal balance		12,263,363		11,665,678		12,263,363		11,665,678		12,423,053
Recorded investment		8,561,924		8,859,798		8,561,924		8,859,798		8,720,339
Average recorded investment		8,625,743		8,900,406		8,690,338		8,925,277		9,644,505
Interest income recognized		51,760		58,244		159,353		118,685		250,008
Financial Asset Originated [Member]
Related allowance		259,723		270,329		259,723		270,329		266,256
Unpaid contractual principal balance		10,020,918		9,610,742		10,020,918		9,610,742		10,273,127
Recorded investment		6,805,310		7,122,736		6,805,310		7,122,736		7,094,524
Average recorded investment		6,863,916		7,147,738		6,924,862		7,172,294		7,774,125
Interest income recognized		38,879		37,232		127,525		77,072		171,476
Financial Asset Acquired [Member]
Related allowance			[1]		[1]		[1]		[1]
Unpaid contractual principal balance	[1]	2,242,445		2,054,936		2,242,445		2,054,936		2,149,926
Recorded investment	[1]	1,756,614		1,737,062		1,756,614		1,737,062		1,625,815
Average recorded investment	[1]	1,761,827		1,752,668		1,765,476		1,752,983		1,870,380
Interest income recognized	[1]	12,881		21,012		31,828		41,613		78,532
Real Estate Loans [Member] | Residential [Member] | Financial Asset Originated [Member]
Unpaid contractual principal balance, with no related allowance recorded		631,126		515,922		631,126		515,922		665,051
Recorded investment, with no related allowance recorded		467,785		379,988		467,785		379,988		517,600
Average recorded investment, with no related allowance recorded		470,171		384,968		477,820		387,950		548,636
Interest income recognized, with no related allowance recorded		3,309		321		4,100		967		9,257
Unpaid contractual principal balance, with an allowance recorded		1,257,297		1,332,333		1,257,297		1,332,333		1,336,078
Recorded investment, with an allowance recorded		1,243,121		1,304,883		1,243,121		1,304,883		1,309,440
Related allowance		257,866		270,329		257,866		270,329		266,256
Average recorded investment, with an allowance recorded		1,245,847		1,316,635		1,250,755		1,317,648		1,328,919
Interest income recognized, with an allowance recorded		12,419		12,748		24,918		25,550		51,928
Real Estate Loans [Member] | Residential [Member] | Financial Asset Acquired [Member]
Unpaid contractual principal balance, with no related allowance recorded	[1]	1,096,210		1,447,903		1,096,210		1,447,903		1,082,484
Recorded investment, with no related allowance recorded	[1]	1,002,307		1,260,264		1,002,307		1,260,264		922,252
Average recorded investment, with no related allowance recorded	[1]	1,005,999		1,271,653		1,008,837		1,277,955		945,602
Interest income recognized, with no related allowance recorded	[1]	5,856		14,444		16,979		27,264		26,437
Unpaid contractual principal balance, with an allowance recorded	[1]
Recorded investment, with an allowance recorded	[1]
Related allowance	[1]
Average recorded investment, with an allowance recorded	[1]
Interest income recognized, with an allowance recorded	[1]
Real Estate Loans [Member] | Investor Loans [Member] | Financial Asset Originated [Member]
Unpaid contractual principal balance, with no related allowance recorded		69,151		9,909		69,151		9,909		126,389
Recorded investment, with no related allowance recorded		27,869		5,294		27,869		5,294		60,949
Average recorded investment, with no related allowance recorded		29,105		5,344		29,690		5,451		118,175
Interest income recognized, with no related allowance recorded										3,772
Unpaid contractual principal balance, with an allowance recorded		53,596				53,596
Recorded investment, with an allowance recorded		31,557				31,557
Related allowance		1,857				1,857
Average recorded investment, with an allowance recorded		31,257				30,479
Interest income recognized, with an allowance recorded
Real Estate Loans [Member] | Investor Loans [Member] | Financial Asset Acquired [Member]
Unpaid contractual principal balance, with no related allowance recorded	[1]	769,766		210,983		769,766		210,983		682,045
Recorded investment, with no related allowance recorded	[1]	499,838		210,988		499,838		210,988		444,254
Average recorded investment, with no related allowance recorded	[1]	501,079		213,788		500,429		206,636		659,246
Interest income recognized, with no related allowance recorded	[1]	4,944		2,999		9,137		6,810		37,368
Unpaid contractual principal balance, with an allowance recorded	[1]
Recorded investment, with an allowance recorded	[1]
Related allowance	[1]
Average recorded investment, with an allowance recorded	[1]
Interest income recognized, with an allowance recorded	[1]
Real Estate Loans [Member] | Commercial [Member] | Financial Asset Originated [Member]
Unpaid contractual principal balance, with no related allowance recorded		6,399,358		6,594,464		6,399,358		6,594,464		6,487,088
Recorded investment, with no related allowance recorded		4,251,209		4,707,655		4,251,209		4,707,655		4,356,264
Average recorded investment, with no related allowance recorded		4,251,209		4,707,655		4,265,903		4,712,233		4,634,504
Interest income recognized, with no related allowance recorded						53,278		1,077		1,077
Unpaid contractual principal balance, with an allowance recorded
Recorded investment, with an allowance recorded
Related allowance
Average recorded investment, with an allowance recorded
Interest income recognized, with an allowance recorded
Real Estate Loans [Member] | Commercial [Member] | Financial Asset Acquired [Member]
Unpaid contractual principal balance, with no related allowance recorded	[1]	246,697		251,573		246,697		251,573		248,938
Recorded investment, with no related allowance recorded	[1]	196,697		201,573		196,697		201,573		198,938
Average recorded investment, with no related allowance recorded	[1]	196,697		202,395		197,398		203,121		201,519
Interest income recognized, with no related allowance recorded	[1]	618		1,900		2,481		3,813		7,336
Unpaid contractual principal balance, with an allowance recorded	[1]
Recorded investment, with an allowance recorded	[1]
Related allowance	[1]
Average recorded investment, with an allowance recorded	[1]
Interest income recognized, with an allowance recorded	[1]
Real Estate Loans [Member] | Commercial Construction [Member] | Financial Asset Originated [Member]
Unpaid contractual principal balance, with no related allowance recorded
Recorded investment, with no related allowance recorded
Average recorded investment, with no related allowance recorded
Interest income recognized, with no related allowance recorded
Unpaid contractual principal balance, with an allowance recorded
Recorded investment, with an allowance recorded
Related allowance
Average recorded investment, with an allowance recorded
Interest income recognized, with an allowance recorded
Real Estate Loans [Member] | Commercial Construction [Member] | Financial Asset Acquired [Member]
Unpaid contractual principal balance, with no related allowance recorded	[1]
Recorded investment, with no related allowance recorded	[1]
Average recorded investment, with no related allowance recorded	[1]
Interest income recognized, with no related allowance recorded	[1]
Unpaid contractual principal balance, with an allowance recorded	[1]
Recorded investment, with an allowance recorded	[1]
Related allowance	[1]
Average recorded investment, with an allowance recorded	[1]
Interest income recognized, with an allowance recorded	[1]
Commercial Portfolio Segment [Member]
Interest income recognized, with no related allowance recorded										103,474
Commercial Portfolio Segment [Member] | Financial Asset Originated [Member]
Unpaid contractual principal balance, with no related allowance recorded		1,595,928		1,109,333		1,595,928		1,109,333		1,562,756
Recorded investment, with no related allowance recorded		769,307		702,352		769,307		702,352		795,410
Average recorded investment, with no related allowance recorded		821,814		710,139		850,675		725,401		1,082,773
Interest income recognized, with no related allowance recorded		23,022		24,086		44,937		49,238
Unpaid contractual principal balance, with an allowance recorded
Recorded investment, with an allowance recorded
Related allowance
Average recorded investment, with an allowance recorded
Interest income recognized, with an allowance recorded
Commercial Portfolio Segment [Member] | Financial Asset Acquired [Member]
Unpaid contractual principal balance, with no related allowance recorded	[1]
Recorded investment, with no related allowance recorded	[1]
Average recorded investment, with no related allowance recorded	[1]
Interest income recognized, with no related allowance recorded	[1]
Unpaid contractual principal balance, with an allowance recorded	[1]
Recorded investment, with an allowance recorded	[1]
Related allowance	[1]
Average recorded investment, with an allowance recorded	[1]
Interest income recognized, with an allowance recorded	[1]
Home Equity Loans [Member] | Financial Asset Originated [Member]
Unpaid contractual principal balance, with no related allowance recorded		7,254		48,781		7,254		48,781		47,650
Recorded investment, with no related allowance recorded		7,254		22,564		7,254		22,564		20,595
Average recorded investment, with no related allowance recorded		7,279		22,997		12,148		23,611		22,604
Interest income recognized, with no related allowance recorded		54		77		133		240		392
Unpaid contractual principal balance, with an allowance recorded
Recorded investment, with an allowance recorded
Related allowance
Average recorded investment, with an allowance recorded
Interest income recognized, with an allowance recorded
Home Equity Loans [Member] | Financial Asset Acquired [Member]
Unpaid contractual principal balance, with no related allowance recorded	[1]	38,310		42,927		38,310		42,927		40,473
Recorded investment, with no related allowance recorded	[1]
Average recorded investment, with no related allowance recorded	[1]
Interest income recognized, with no related allowance recorded	[1]	329		313		650		600		1,329
Unpaid contractual principal balance, with an allowance recorded	[1]
Recorded investment, with an allowance recorded	[1]
Related allowance	[1]
Average recorded investment, with an allowance recorded	[1]
Interest income recognized, with an allowance recorded	[1]
Consumer Portfolio Segment [Member] | Financial Asset Originated [Member]
Unpaid contractual principal balance, with no related allowance recorded		7,208				7,208				48,115
Recorded investment, with no related allowance recorded		7,208				7,208				34,266
Average recorded investment, with no related allowance recorded		7,234				7,392				38,514
Interest income recognized, with no related allowance recorded		75				159				1,576
Unpaid contractual principal balance, with an allowance recorded
Recorded investment, with an allowance recorded
Related allowance
Average recorded investment, with an allowance recorded
Interest income recognized, with an allowance recorded
Consumer Portfolio Segment [Member] | Financial Asset Acquired [Member]
Unpaid contractual principal balance, with no related allowance recorded	[1]	91,462		101,550		91,462		101,550		95,986
Recorded investment, with no related allowance recorded	[1]	57,772		64,237		57,772		64,237		60,371
Average recorded investment, with no related allowance recorded	[1]	58,052		64,832		58,812		65,271		64,013
Interest income recognized, with no related allowance recorded	[1]	1,134		1,356		2,581		3,126		6,062
Unpaid contractual principal balance, with an allowance recorded	[1]
Recorded investment, with an allowance recorded	[1]
Related allowance	[1]
Average recorded investment, with an allowance recorded	[1]
Interest income recognized, with an allowance recorded	[1]

[1] Generally accepted accounting principles require that we record acquired loans at fair value at acquisition, which includes a discount for loans with credit impairment. These purchased credit impaired loans are not performing according to their contractual terms and meet the definition of an impaired loan. Although we do not accrue interest income at the contractual rate on these loans, we do recognize an accretable yield as interest income to the extent such yield is supported by cash flow analysis of the underlying loans.