Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2018	May 31, 2017
Earnings Per Share [Abstract]
Net income	$ 21,576	$ 18,751	$ 52,613	$ 42,832
Weighted average common shares outstanding– basic (in shares)	36,924	42,402	38,178	43,972
Effect of dilutive employee stock options and unvested restricted stock units (in shares)	392	691	455	757
Weighted average common shares outstanding – diluted (in shares)	37,316	43,093	38,633	44,729
Net income per common share – basic (usd per share)	$ 0.58	$ 0.44	$ 1.38	$ 0.97
Net income per common share – diluted (usd per share)	$ 0.58	$ 0.44	$ 1.36	$ 0.96
Anti-dilutive securities excluded (in shares)	1,898	1,362	1,534	1,095