Restructuring Charges - Additional Information (Detail) (USD $)	3 Months Ended
	Dec. 28, 2012	Dec. 28, 2012 Fiscal 2012 Restructuring Plan	Dec. 28, 2012 Fiscal 2012 Restructuring Plan Minimum	Dec. 28, 2012 Fiscal 2012 Restructuring Plan Maximum	Sep. 30, 2012 Fiscal 2011 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1,471,000	$ 2,300,000
Restructuring charges related to severance costs		2,100,000			1,200,000
Contractual obligations on vacated space		206,000
Total charges incurred			4,000,000	5,000,000
Cash expenditure incurred			$ 3,500,000	$ 4,500,000