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Capital Stock (Details) - shares	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Outstanding Shares [Roll Forward]
Shares outstanding	157,332,121	158,590,383	161,693,051
Exercised stock options	726,636	851,628	905,834
Exercise of employee stock purchase plan	167,806	150,669	150,174
Vesting of restricted stock units, net of shares withheld for taxes	200,431	232,875	262,488
Treasury Stock, Shares, Acquired		(6,475)
Shares outstanding	157,462,140	157,332,121	158,590,383
Stock repurchased under buyback program	(1,074,234)	(2,573,475)	(4,581,227)
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period		86,516
Performance Shares [Member]
Outstanding Shares [Roll Forward]
Settlement of performance-based restricted stock units, net of shares withheld for taxes	332,875	146,061
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	109,380		160,063

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Outstanding Shares [Roll Forward]

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Number, after shares used to satisfy grantee's tax withholding obligation for award under share-based payment arrangement, of restricted shares issued. Excludes cash used to satisfy grantee's tax withholding obligation.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Number of shares issued under share-based payment arrangement.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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Number of share options (or share units) exercised during the current period.

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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