Cash Dividends Declared to Common Stockholders (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Aug. 31, 2014 October 17, 2013	Aug. 31, 2014 January 22, 2014	Aug. 31, 2014 April 17, 2014	Aug. 31, 2014 July 23, 2014	Aug. 31, 2013 October 16, 2012	Aug. 31, 2013 January 23, 2013	Aug. 31, 2013 April 15, 2013	Aug. 31, 2013 July 18, 2013
Dividends [Line Items]
Dividend Declaration Date	Oct. 17, 2013	Jan. 22, 2014	Apr. 17, 2014	Jul. 23, 2014	Oct. 16, 2012	Jan. 23, 2013	Apr. 15, 2013	Jul. 18, 2013
Dividend per Share	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08	$ 0.08
Total of Cash Dividends Declared	$ 17,221	$ 16,976	$ 16,686	$ 16,289	$ 16,962	$ 16,990	$ 16,994	$ 17,005
Date of Record for Dividend Payment	Nov. 15, 2013	Feb. 14, 2014	May 15, 2014	Aug. 15, 2014	Nov. 15, 2012	Feb. 15, 2013	May 15, 2013	Aug. 15, 2013
Dividend Cash Payment Date	Dec. 02, 2013	Mar. 03, 2014	Jun. 02, 2014	Sep. 02, 2014	Dec. 03, 2012	Mar. 01, 2013	Jun. 03, 2013	Sep. 03, 2013