Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2017	Feb. 29, 2016
Earnings Per Share [Abstract]
Net income	$ 10,963	$ 10,819	$ 24,081	$ 23,277
Weighted average common shares outstanding– basic (in shares)	43,794	48,977	44,757	49,599
Effect of dilutive employee stock options and unvested restricted stock units (in shares)	756	1,011	790	1,057
Weighted average common shares outstanding – diluted (in shares)	44,550	49,988	45,547	50,656
Net income per common share – basic (usd per share)	$ 0.25	$ 0.22	$ 0.54	$ 0.47
Net income per common share – diluted (usd per share)	$ 0.25	$ 0.22	$ 0.53	$ 0.46
Anti-dilutive securities excluded (in shares)	1,100	552	961	482