Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Earnings Per Share [Abstract]
Net income	$ 19,607	$ 10,963	$ 31,037	$ 24,081
Weighted average common shares outstanding– basic (in shares)	38,284	43,794	38,806	44,757
Effect of dilutive employee stock options and unvested restricted stock units (in shares)	413	756	485	790
Weighted average common shares outstanding – diluted (in shares)	38,697	44,550	39,291	45,547
Net income per common share – basic (usd per share)	$ 0.51	$ 0.25	$ 0.80	$ 0.54
Net income per common share – diluted (usd per share)	$ 0.51	$ 0.25	$ 0.79	$ 0.53
Anti-dilutive securities excluded (in shares)	1,417	1,100	1,352	961