Stock-Based Compensation and Shares Repurchases - Common Stock Shares Outstanding (Details) - shares	3 Months Ended		6 Months Ended
	Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance (in shares)			164,588,172
Ending Balance (in shares)	152,878,329		152,878,329
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance (in shares)	157,986,896	176,305,660	164,588,172	177,727,653
Shares issued upon exercise of stock options (in shares)	11,348	154	11,348	29,688
Shares issued under employee stock purchase plan (in shares)	691,971	575,516	692,325	575,516
Vesting of restricted stock (in shares)	219,764	220,022	1,905,927	2,694,147
Purchases of treasury stock under employee stock plans (in shares)	(57,389)	(59,708)	(464,836)	(784,031)
Treasury shares purchased (in shares)	(5,974,261)	(4,978,414)	(13,854,607)	(8,179,743)
Ending Balance (in shares)	152,878,329	172,063,230	152,878,329	172,063,230