Stock-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares authorized by the Plan	750,000
Dividend yield	0.00%
Options granted in period	0	0	0
Intrinsic value of options exercised	$ 13,000	$ 518,000	$ 173,000
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	32,000	608,000	184,000
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options term	10 years
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense associated with stock awards	821,000	1,307,000	883,000
Restricted stock grants	0	0	103,500
Grant date fair value of the restricted stock awards			$ 23.55
Vesting year	2015
Unrecognized compensation cost related to nonvested stock awards	552,000
Nonvested awards, compensation cost not yet recognized, weighted average period for recognition	8 months 9 days
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense associated with stock awards	0	62,000	362,000
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense associated with stock awards	233,000	25,000	0
Restricted stock grants	21,411	2,000
Grant date fair value of the restricted stock awards	$ 31.91	$ 27.14
Unrecognized compensation cost related to nonvested stock awards	486,000
Restricted stock units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested awards, compensation cost not yet recognized, weighted average period for recognition	2 years 1 month 21 days
Common Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense associated with stock awards	$ 171,000	$ 403,000	$ 244,000
Restricted stock grants	5,515	14,484	7,234
Grant date fair value of the restricted stock awards	$ 30.99	$ 27.83	$ 33.64

Share Based Compensation Arrangement by Share Based Payment Award Equity Instruments Other Than Options Vesting Year

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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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Aggregate proceeds received by the entity during the annual period from exercises of stock or unit options and conversion of similar instruments granted under equity-based payment arrangements.

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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 share-based awards, other than options, awarded to employees as compensation.

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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 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).

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The weighted average fair value at grant date for nonvested equity-based awards issued 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).

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

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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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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