Equity Award Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Sep. 30, 2013 Executives Award	Sep. 30, 2012	Sep. 30, 2011	Dec. 09, 2007
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Number of equity award plans	3
Options unavailable for grant upon expiration of 1987 Plan				521,354
Share-based payment award, expiration period	10 years
Restricted stock, shares vested to non-employee director	4,000
Number of options granted with exercise price less than fair market value on grant date	0
Total intrinsic value of options exercised	$ 2,080,000	$ 1,544,000	$ 9,659,000
Proceeds from exercise of stock options	744,000	107,000	2,285,000
Actual tax benefit realized for tax deductions from option exercised	784,000	580,000	3,617,000
Exercise of stock options, shares	163,000
Exercise of stock options, net	744,000	107,000	2,285,000
Net-share settled by company	39,934	51,041	109,926
Weighted average fair value of stock options	$ 7.98	$ 6.17	$ 9.69
Cumulative operating income during performance period, fiscal 2012 through fiscal 2014, minimum	109,582,000	120,000,000
Maximum Cumulative Operating Income During Performance Period	132,201,000	132,000,000
Number of executive officers granted performance based RSU	4
Unrecognized compensation cost	5,143,000
Weighted-average period recognized compensation cost	1 year 3 months 18 days
Repurchase of common stock, shares	34,125	30,849	128,646
Payments for tax obligations to the tax authorities on exercise or vesting date	725,000	597,000	2,786,000
Minimum
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Share-based payment award, vesting period	4 years
Minimum | Executive | RSUs
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Cumulative restricted stock units available for future declaration	18,541	19,531
Maximum
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Share-based payment award, vesting period	5 years
Maximum | Executive | RSUs
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Cumulative restricted stock units available for future declaration	55,621	58,590
1987 Plan
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Options to be issued	4,350,000
2005 Plan
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Options to be issued	2,800,000
Common stock shares issued, restricted stock units under 2005 Plan	1,500,000
Common stock available for grant under the 2005 Plan	1,095,106
Shares issued in respect of restricted stock under the 2005 Plan	641,347
Exercise of stock options, shares	101,949	119,600	368,800
Exercise of stock options, net	$ 890,000	$ 1,007,000	$ 2,428,000
2005 Plan | Minimum
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Share-based payment award, expiration period	1 year
2005 Plan | Maximum
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Share-based payment award, expiration period	5 years
Director Plan
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Share based compensation arrangement by share based payment award number of shares authorized to be issued as stock options	400,000
Non-executive chairman
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Restricted stock, shares vested to non-employee director	6,000