Common Stock and Earnings Per Share - Weighted Average Shares Outstanding (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Basic EPS
Net Income (Numerator)	$ 88,686	$ 84,702	$ 182,643	$ 168,998
Weighted Average Common Shares (Denominator)	37,875	38,055	37,927	38,081
Per Share Amount	$ 2.34	$ 2.23	$ 4.82	$ 4.44
Diluted EPS
Weighted Average Common Shares (Denominator)	701	564	655	633
Income available to common stockholders plus assumed conversions, net income amount	$ 88,686	$ 84,702	$ 182,643	$ 168,998
Income available to common stockholders plus assumed conversion, weighted average common shares (in shares)	38,576	38,619	38,582	38,714
Income available to common stockholders plus assumed conversions, per share amount (in dollars per share)	$ 2.30	$ 2.19	$ 4.73	$ 4.37
Basic earnings per common share (in USD per share)	2.34	2.23	4.82	4.44
Diluted earnings per common share (in USD per share)	$ 2.30	$ 2.19	$ 4.73	$ 4.37