Note 5 - Fair Value of Financial Instruments - Fair Value of Available-for-sale Securities (Details) - USD ($)	Dec. 31, 2018	Mar. 31, 2018
Total	$ 75,268,216	$ 77,554,999
Less than 1 year	23,360,664
1-3 years	22,867,445
3-5 years	$ 29,040,107

Fair value of available-for-sale debt securities maturing after three through five years.

No definition available.

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- Definition

Fair value of available-for-sale debt securities maturing in one to three years.

+ References

No definition available.

+ Details

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- Definition

Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), maturing in next fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=75019621&loc=d3e62586-112803

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
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