Note 12 - Stockholders' Equity (Details) - Dividends Declared During the Period (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
	May 31, 2014
May 5, 2014 Declaration Date [Member]
Note 12 - Stockholders' Equity (Details) - Dividends Declared During the Period [Line Items]
Dividends Per Share of Common Stock	$ 0.39
Record Date	May 30, 2014
Total $ Amount	$ 16,386
Payment Date	Jun. 17, 2014
February 11, 2014 Declaration Date [Member]
Note 12 - Stockholders' Equity (Details) - Dividends Declared During the Period [Line Items]
Dividends Per Share of Common Stock	$ 0.35
Record Date	Feb. 28, 2014
Total $ Amount	14,827
Payment Date	Mar. 18, 2014
November 14, 2013 Declaration Date [Member]
Note 12 - Stockholders' Equity (Details) - Dividends Declared During the Period [Line Items]
Dividends Per Share of Common Stock	$ 0.35
Record Date	Nov. 29, 2013
Total $ Amount	15,046
Payment Date	Dec. 17, 2013
August 15, 2013 Declaration Date [Member]
Note 12 - Stockholders' Equity (Details) - Dividends Declared During the Period [Line Items]
Dividends Per Share of Common Stock	$ 0.35
Record Date	Aug. 31, 2013
Total $ Amount	15,164
Payment Date	Sep. 17, 2013
May 14, 2013 Declaration Date [Member]
Note 12 - Stockholders' Equity (Details) - Dividends Declared During the Period [Line Items]
Dividends Per Share of Common Stock	$ 0.35
Record Date	May 31, 2013
Total $ Amount	15,413
Payment Date	Jun. 18, 2013
February 21, 2013 Declaration Date [Member]
Note 12 - Stockholders' Equity (Details) - Dividends Declared During the Period [Line Items]
Dividends Per Share of Common Stock	$ 0.31
Record Date	Feb. 28, 2013
Total $ Amount	13,510
Payment Date	Mar. 19, 2013
November 15, 2012 Declaration Date [Member]
Note 12 - Stockholders' Equity (Details) - Dividends Declared During the Period [Line Items]
Dividends Per Share of Common Stock	$ 0.31
Record Date	Nov. 30, 2012
Total $ Amount	13,746
Payment Date	Dec. 18, 2012
August 8, 2012 Declaration Date [Member]
Note 12 - Stockholders' Equity (Details) - Dividends Declared During the Period [Line Items]
Dividends Per Share of Common Stock	$ 0.31
Record Date	Aug. 31, 2012
Total $ Amount	13,727
Payment Date	Sep. 18, 2012
May 8, 2012 Declaration Date [Member]
Note 12 - Stockholders' Equity (Details) - Dividends Declared During the Period [Line Items]
Dividends Per Share of Common Stock	$ 0.31
Record Date	May 31, 2012
Total $ Amount	$ 13,893
Payment Date	Jun. 19, 2012