Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Feb. 28, 2015		Feb. 28, 2014		Feb. 28, 2015		Feb. 28, 2014
Earnings Per Share [Abstract]
Net income	$ 7,662		$ 4,107		$ 17,747		$ 12,315
Weighted average common shares outstanding – basic	53,171		55,958		53,226		56,125
Effect of dilutive employee stock options and unvested restricted stock units	1,489		1,450		1,518		1,528
Weighted average common shares - diluted	54,660		57,408		54,744		57,653
Net income per common share - basic	$ 0.14		$ 0.07		$ 0.33		$ 0.22
Net income per common share - diluted	$ 0.14		$ 0.07		$ 0.32		$ 0.21
Anti-dilutive securities excluded	173	[1]	1,117	[1]	313	[1]	1,042	[1]

[1] Anti-dilutive securities consist of stock options and unvested restricted stock units that were not included in the computation of diluted earnings per share because either the exercise price of the options was greater than the average market price of the common stock or the total assumed proceeds under the treasury stock method resulted in negative incremental shares and thus the inclusion would have been anti-dilutive.