Summary of Activity Related to Target Number of Shares Awarded and Actual Number of Shares Earned Under 2007 Plan (Detail) (2007 Plan, USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Dec. 31, 2012
Schedule Of Stock Options [Line Items]
Beginning Balance, Outstanding number of shares	158
Shares awarded, Number of shares award forfeited (various awards)	(28)
Ending Balance, Outstanding number of shares	150
Beginning Balance, Outstanding weighted average fair value at date of grant	$ 18.30
Shares not earned, Weighted average fair value at date of grant awards forfeited (various awards)	$ 17.00
Ending Balance, Outstanding weighted average fair value at date of grant	$ 18.30
Performance shares
Schedule Of Stock Options [Line Items]
Shares awarded, Number of shares 2013 award	49
Shares earned, Number of shares 2010 award	(29)
Shares earned, Weighted average fair value at date of grant 2010 award	$ 16.03
Shares not earned, Weighted average fair value at date of grant 2010 award	$ 15.75

Summary of Activity Related to Target Number of Shares Awarded and Actual Number of Shares Earned Under 2007 Plan (Detail) (2007 Plan, USD $)
In Thousands, except Per Share data, unless otherwise specified

3 Months Ended

Dec. 31, 2012

Schedule Of Stock Options [Line Items]

Beginning Balance, Outstanding number of shares

158

Shares awarded, Number of shares award forfeited (various awards)

(28)

Ending Balance, Outstanding number of shares

150

Beginning Balance, Outstanding weighted average fair value at date of grant

$ 18.30

Shares not earned, Weighted average fair value at date of grant awards forfeited (various awards)

$ 17.00

Ending Balance, Outstanding weighted average fair value at date of grant

$ 18.30

Performance shares

Schedule Of Stock Options [Line Items]

Shares awarded, Number of shares 2013 award

Shares earned, Number of shares 2010 award

(29)

Shares earned, Weighted average fair value at date of grant 2010 award

$ 16.03

Shares not earned, Weighted average fair value at date of grant 2010 award

$ 15.75

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- Definition

Share-based compensation arrangement by share-based payment award equity instruments other than options earned weighted average grant date fair value.

+ References

No definition available.

+ Details

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- Definition

Share-based compensation arrangement by share-based payment award equity instruments other than options not earned weighted average grant date fair value.

+ References

No definition available.

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- Definition

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

+ References

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

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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

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ 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)(i)-(ii)

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(b)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(a)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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- Definition

Number of share instruments newly issued under a share-based compensation 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

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 65

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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