Common Stock and Earnings Per Share - Weighted Average Shares Outstanding (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2020	May 31, 2019
Basic EPS
Net Income (Numerator)	$ 101,216	$ 92,265	$ 283,859	$ 261,263
Weighted Average Common Shares (Denominator) (in shares)	37,885	38,223	37,912	38,128
Per Share Amount (in USD per share)	$ 2.67	$ 2.41	$ 7.49	$ 6.85
Diluted EPS
Weighted Average Common Shares (Denominator) (in shares)	596	770	636	679
income available to common stockholders plus assumed conversions, Net Income (Numerator)	$ 101,216	$ 92,265	$ 283,859	$ 261,263
income available to common stockholders plus assumed conversions, Weighted Average Common Shares (Denominator) (in shares)	38,481	38,993	38,548	38,807
income available to common stockholders plus assumed conversions, Per Share Amount (in USD per share)	$ 2.63	$ 2.37	$ 7.36	$ 6.73