Note 4 - Marketable Securities (Details Textual)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Total	19
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 9,072,719
Number of Other-than-temporarily Impaired Marketable Securities	0

Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant