Note 10 - Subsequent Events (Details Textual) - $ / shares		3 Months Ended
Jul. 18, 2018	Jun. 30, 2018	Jun. 30, 2017
Common Stock, Dividends, Per Share, Declared		$ 1	$ 1
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared	$ 1
Subsequent Event [Member] \| Common Stock [Member]
Dividends Payable, Date to be Paid	Aug. 31, 2018
Dividends Payable, Date of Record	Jul. 30, 2018

Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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Date the declared dividend will be paid, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

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