Stockholders' Equity And Stock-Based Compensation (Schedule Of Stock-Based Compensation Expense By Plan) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 27, 2020	Mar. 29, 2019	Mar. 27, 2020	Mar. 29, 2019
Stockholders' Equity And Stock-Based Compensation [Line Items]
Stock-based compensation expense	$ 20,951	$ 19,235	$ 43,565	$ 40,717
Share-based Compensation			43,565	40,717
Benefit from income taxes	(3,521)	(3,465)	(7,115)	(7,225)
Total stock-based compensation, net of tax	17,430	15,770	36,450	33,492
Stock Option [Member]
Stockholders' Equity And Stock-Based Compensation [Line Items]
Stock-based compensation expense	3,974	4,279	8,520	9,301
Restricted Stock Units (RSUs) [Member]
Stockholders' Equity And Stock-Based Compensation [Line Items]
Stock-based compensation expense	15,850	13,895	32,817	29,270
Employee Stock Purchase Plan [Member]
Stockholders' Equity And Stock-Based Compensation [Line Items]
Stock-based compensation expense	1,127	1,061	2,228	2,146
Cost of Sales [Member]
Stockholders' Equity And Stock-Based Compensation [Line Items]
Stock-based compensation expense	507	412	1,050	900
Research and Development Expense [Member]
Stockholders' Equity And Stock-Based Compensation [Line Items]
Stock-based compensation expense	6,179	5,785	13,166	12,026
Selling and Marketing Expense [Member]
Stockholders' Equity And Stock-Based Compensation [Line Items]
Stock-based compensation expense	7,702	7,217	15,876	15,434
General and Administrative Expense [Member]
Stockholders' Equity And Stock-Based Compensation [Line Items]
Stock-based compensation expense	$ 6,563	$ 5,821	$ 13,473	$ 12,357