Note 5 - Fair Value of Financial Instruments - Investment Securities With Unrealized Losses (Details) - USD ($)	Sep. 30, 2019	Mar. 31, 2019
Fair market value, less than 12 months
Gross unrealized losses, less than 12 months
Fair market value, 12 months or greater	5,054,583	51,413,428
Gross unrealized losses, 12 months or greater	(26,360)	(421,798)
Total fair market value	5,054,583	51,413,428
Total gross unrealized losses	(26,360)	(421,798)
Corporate Bond Securities [Member]
Fair market value, less than 12 months
Gross unrealized losses, less than 12 months
Fair market value, 12 months or greater	5,054,583	51,413,428
Gross unrealized losses, 12 months or greater	(26,360)	(421,798)
Total fair market value	5,054,583	51,413,428
Total gross unrealized losses	$ (26,360)	$ (421,798)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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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), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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