Share-Based Compensation Awards Granted (Detail) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options		98,186	0
Total share-based awards	627,418	311,962	389,604
Aggregate fair value at grant dates	$ 17.0	$ 17.5	$ 17.5
Dividend Declared [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options	0
Employees \| Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options	440,690	0	0
Employees \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation awards granted	78,463	112,315	178,030
Employees \| Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation awards granted	78,352	161,229	178,321
Board of Directors Chairman \| Deferred Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation awards granted	29,913	38,418	33,253

Total Grants of Share-Based Compensation Awards.

No definition available.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Net number of share options (or share units) granted during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Value, after forfeitures, of stock or other type of equity granted of any equity-based compensation plan other than an employee stock ownership plan (ESOP).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 30

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=51830203&loc=d3e3913-113898

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-Publisher FASB

-Name Accounting Standards Codification

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