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Capital Stock (Details) - shares	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Outstanding Shares [Roll Forward]
Shares outstanding	161,693,051	160,497,841	159,760,671
Exercised stock options	905,834	270,599	506,632
Exercise of employee stock purchase plan	150,174	218,475	212,550
Vesting of restricted stock units, net of shares withheld for taxes	262,488	370,138	541,839
Shares outstanding	158,590,383	161,693,051	160,497,841
Stock repurchased under buyback program	(4,581,227)		(523,851)
Performance Shares [Member]
Outstanding Shares [Roll Forward]
Exercise of employee stock purchase plan	160,063
Vesting of restricted stock units, net of shares withheld for taxes		335,998

X

- Definition

Outstanding Shares [Roll Forward]

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Topic 505
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-Section 50
-Paragraph 2
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X

- Definition

The number of restricted shares issued as compensation, net of shares for the payment of withholding taxes. This element is to be used only if shares are used in lieu of cash to satisfy all or a portion of withholding taxes.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644

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

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Topic 210
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