Interest Expense Information Related to Convertible Senior Notes (Detail) (USD $)	3 Months Ended
	Dec. 28, 2012	Dec. 30, 2011
Debt Instrument [Line Items]
Interest expense - coupon	$ 306,000
Interest expense - debt discount amortization	244,000	144,000
6.75% Convertible Senior Notes
Debt Instrument [Line Items]
Interest expense - coupon	548,000
Interest expense - debt discount amortization	80,000
Total	628,000
Effective interest rate on the liability for the period	7.85%	0.00%
6.50% Convertible Senior Notes
Debt Instrument [Line Items]
Interest expense - coupon	244,000	245,000
Interest expense - debt discount amortization	106,000	102,000
Total	$ 350,000	$ 347,000
Effective interest rate on the liability for the period	9.33%	9.25%