Stock Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares authorized by the Plan	750,000
Intrinsic value of options exercised	$ 518,000	$ 173,000	$ 318,000
Fair value of options vested	362,000	362,000	362,000
Outstanding options, expiration date	Dec. 31, 2018
Outstanding options, exercise price	$ 18.91	$ 18.91
Unrecognized compensation cost related to nonvested stock option awards	0
Excess tax benefit from disqualifying dispositions	0	0	0
Cash received from option exercises under all share-based payment arrangements	608,000	184,000	297,000
Compensation expense associated with stock option awards	403,000	244,000	186,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense associated with stock option awards	62,000	362,000	362,000
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to nonvested stock option awards	1,337,000
Compensation expense associated with stock option awards	1,307,000	883,000	1,123,000
Restricted stock grants	0	103,500	0
Grant date fair value of the restricted stock awards	$ 23.55	$ 23.45
Nonvested Awards, Compensation Cost Not yet Recognized, Weighted average Period for Recognition	1 year 8 months 9 days
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to nonvested stock option awards	29,000
Compensation expense associated with stock option awards	$ 25,000
Restricted stock grants	2,000
Grant date fair value of the restricted stock awards	$ 27.14
Nonvested Awards, Compensation Cost Not yet Recognized, Weighted average Period for Recognition	9 months 22 days

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.

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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.

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Unrecognized cost of unvested options awarded to employees as compensation.

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Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

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The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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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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Date the equity-based award expires, in CCYY-MM-DD format.

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Net number of non-option equity instruments granted to participants.

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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).

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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