Stock-Based Compensation - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
Dec. 31, 2014	Dec. 31, 2013
2007 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, vesting period (in years)	10 years
Aggregate number of shares that may be awarded	600,000
Performance period (in years)	3 years
Stock options may be awarded (in shares)	263,000
Compensation expense related to performance and restricted shares awarded	$ 529	$ 238
Total unrecognized compensation cost related to performance and restricted shares awarded	$ 2,882
Period of recognized compensation cost (in years)	2 years 9 months
2007 Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares earned as percentage of initial target number shares awarded	150.00%
Outstanding share awards earned and issued at greater than the target number of shares	150.00%
Performance shares \| 2007 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, vesting period (in years)	3 years
Share granted (in shares)	45,000
Granted shares fair value (in dollars per share)	$ 30.57
Restricted shares \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, vesting period (in years)	1 year
Restricted shares \| 2007 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, vesting period (in years)	1 year
Share granted (in shares)	16,000
Granted shares fair value (in dollars per share)	$ 30.57

Common shares earned percentage of initial target number shares awarded.

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- Definition

Outstanding share awards earned and issued at greater than the target number of shares.

+ References

No definition available.

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- Definition

Share based compensation arrangement by share based payment award performance period.

+ References

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section S99

-Paragraph 1

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ 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 (i)

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

No definition available.

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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-Paragraph 2

-Subparagraph (a)(1)

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ 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 (a)(3)

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

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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- Definition

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

+ References

No definition available.

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

+ References

No definition available.

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