Capital Stock (Details) - shares	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Outstanding Shares [Roll Forward]
Shares outstanding	157,462,140	157,332,121	158,590,383
Exercised stock options	534,291	726,636	851,628
Exercise of employee stock purchase plan	182,971	167,806	150,669
Vesting of restricted stock units, net of shares withheld for taxes	242,112	200,431	232,875
Treasury Stock, Shares, Acquired			(6,475)
Shares outstanding	158,064,750	157,462,140	157,332,121
Stock repurchased under buyback program	(418,374)	(1,074,234)	(2,573,475)
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period		109,380
Performance Shares [Member]
Outstanding Shares [Roll Forward]
Settlement of performance-based restricted stock units, net of shares withheld for taxes	93,647,000,000	181,065
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	61,610		86,516