Capital Stock (Changes in Common Shares) (Details) - shares	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Changes in Common Shares [Roll Forward]
Balance, beginning of year (shares)	220,415,262	219,515,245	218,346,074
Issuance of treasury shares for stock option and award plans (shares)	602,197	900,017	1,169,171
Balance, end of year (shares)	221,017,459	220,415,262	219,515,245

Number, after forfeiture, of shares or units issued under share-based payment arrangement. Excludes shares or units issued under employee stock ownership plan (ESOP).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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