Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Nov. 30, 2017	Nov. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 11,430	$ 13,118
Weighted average common shares outstanding– basic (in shares)	39,327	45,720
Effect of dilutive employee stock options and unvested restricted stock units (in shares)	558	823
Weighted average common shares outstanding – diluted (in shares)	39,885	46,543
Net income per common share – basic (usd per share)	$ 0.29	$ 0.29
Net income per common share – diluted (usd per share)	$ 0.29	$ 0.28
Anti-dilutive securities excluded (in shares)	1,288	821