Note 11. Stockholders' Equity (Detail) - Dividends Declared During the Period (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Nov. 30, 2011
Total $ Amount (in thousands) (in Dollars)	$ 12,200
November 10, 2011 [Member]
Dividends Per Share of Common Stock (in Dollars per share)	$ 0.27
Record Date	Nov. 30, 2011
Total $ Amount (in thousands) (in Dollars)	12,181
Payment Date	Dec. 20, 2011
August 11, 2011 [Member]
Dividends Per Share of Common Stock (in Dollars per share)	$ 0.27
Record Date	Aug. 31, 2011
Total $ Amount (in thousands) (in Dollars)	12,165
Payment Date	Sep. 20, 2011
May 9, 2011 [Member]
Dividends Per Share of Common Stock (in Dollars per share)	$ 0.27
Record Date	May 31, 2011
Total $ Amount (in thousands) (in Dollars)	12,374
Payment Date	Jun. 21, 2011
February 9, 2011 [Member]
Dividends Per Share of Common Stock (in Dollars per share)	$ 0.23
Record Date	Feb. 28, 2011
Total $ Amount (in thousands) (in Dollars)	10,612
Payment Date	Mar. 15, 2011
November 10, 2010 [Member]
Dividends Per Share of Common Stock (in Dollars per share)	$ 0.23
Record Date	Nov. 30, 2010
Total $ Amount (in thousands) (in Dollars)	10,660
Payment Date	Dec. 21, 2010
August 10, 2010 [Member]
Dividends Per Share of Common Stock (in Dollars per share)	$ 0.23
Record Date	Aug. 31, 2010
Total $ Amount (in thousands) (in Dollars)	10,586
Payment Date	Sep. 21, 2010
May 14, 2010 [Member]
Dividends Per Share of Common Stock (in Dollars per share)	$ 0.23
Record Date	May 28, 2010
Total $ Amount (in thousands) (in Dollars)	10,655
Payment Date	Jun. 15, 2010
February 9, 2010 [Member]
Dividends Per Share of Common Stock (in Dollars per share)	$ 0.20
Record Date	Feb. 26, 2010
Total $ Amount (in thousands) (in Dollars)	9,329
Payment Date	Mar. 16, 2010
November 10, 2009 [Member]
Dividends Per Share of Common Stock (in Dollars per share)	$ 0.20
Record Date	Nov. 30, 2009
Total $ Amount (in thousands) (in Dollars)	$ 9,423
Payment Date	Dec. 15, 2009