Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		May. 31, 2015	May. 31, 2014	May. 31, 2015	May. 31, 2014
Earnings Per Share [Abstract]
Net income		$ 20,442	$ 16,776	$ 38,189	$ 29,091
Weighted average common shares outstanding – basic		52,022	54,382	52,851	55,544
Effect of dilutive employee stock options and unvested restricted stock units		1,369	1,371	1,442	1,476
Weighted average common shares - diluted		53,391	55,753	54,293	57,020
Net income per common share - basic		$ 0.39	$ 0.31	$ 0.72	$ 0.52
Net income per common share - diluted		$ 0.38	$ 0.30	$ 0.70	$ 0.51
Anti-dilutive securities excluded	[1]	379	1,025	335	1,036

[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.