Note 12 - Fair Value Measurements - Reconciliation of Investments at Fair Value on Recurring Basis (Details) - USD ($)	6 Months Ended	12 Months Ended
Sep. 30, 2018	Mar. 31, 2018
Balance, beginning of year	$ 1,954,092	$ 1,930,786
Change in valuation	(4,944)
Balance, end of year	1,949,132	1,954,092
Corporate Bond Securities [Member]
Transfers in		1,954,076
Transfers out
Collateralized Mortgage Backed Securities [Member]
Transfers in		16
Transfers out	16	2,473
Municipal Bonds [Member]
Transfers in
Transfers out		$ 1,928,313

Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
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- Definition

Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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