Stock-Based Compensation by Functional Line Item (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 28, 2012	Dec. 30, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 2,671	$ 2,150
Cost of Goods Sold
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	45	(43)
Research and Development Expense
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	913	652
Selling, General and Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 1,713	$ 1,541