Note 14 - Stockholders' Equity - Dividends Declared (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017
Dividends Per Share of Common Stock (in dollars per share)	$ 0.72	$ 0.72	$ 0.64	$ 0.64	$ 0.64	$ 0.64	$ 0.56	$ 0.56
Record Date	Aug. 30, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017
Total $ Amount	$ 27,445	$ 27,506	$ 24,385	$ 24,372	$ 24,443	$ 24,566	$ 21,799	$ 21,902
Payment Date	Sep. 19, 2019	Jun. 18, 2019	Mar. 19, 2019	Dec. 18, 2018	Sep. 18, 2018	Jun. 19, 2018	Mar. 20, 2018	Dec. 19, 2017

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

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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Amount of paid and unpaid cash dividends declared for classes of stock, for example, but not limited to, common and preferred.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817

Reference 2: 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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The per share amount of a dividend declared, but not paid, as of the financial reporting date.

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Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

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