Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		May 31, 2016	May 31, 2015	May 31, 2016	May 31, 2015
Earnings Per Share [Abstract]
Net income		$ 15,353	$ 20,442	$ 38,630	$ 38,189
Weighted average common shares outstanding – basic		48,377	52,022	49,192	52,851
Effect of dilutive employee stock options and unvested restricted stock units		949	1,369	1,021	1,442
Weighted average common shares outstanding - diluted		49,326	53,391	50,213	54,293
Net income per common share - basic		$ 0.32	$ 0.39	$ 0.79	$ 0.72
Net income per common share - diluted		$ 0.31	$ 0.38	$ 0.77	$ 0.70
Anti-dilutive securities excluded	[1]	686	379	550	335

[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.