Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2017	May 31, 2016
Earnings Per Share [Abstract]
Net income	$ 18,751	$ 15,353	$ 42,832	$ 38,630
Weighted average common shares outstanding– basic (in shares)	42,402	48,377	43,972	49,192
Effect of dilutive employee stock options and unvested restricted stock units (in shares)	691	949	757	1,021
Weighted average common shares outstanding – diluted (in shares)	43,093	49,326	44,729	50,213
Net income per common share – basic (usd per share)	$ 0.44	$ 0.32	$ 0.97	$ 0.79
Net income per common share – diluted (usd per share)	$ 0.44	$ 0.31	$ 0.96	$ 0.77
Anti-dilutive securities excluded (in shares)	1,362	686	1,095	550