Stockholders' Equity And Stock-Based Compensation (Schedule of Stock-Based Compensation By Classification) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 29, 2017	Sep. 30, 2016	Sep. 25, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Recognized tax benefit from the exercise of ISO and ESPP	$ 802	$ 550	$ 328
Stock-based compensation expense	65,343	66,985	67,069
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	18,959	19,627	19,606
Allocated Share-based Compensation Expense, Net of Tax	46,384	47,358	47,463
Cost of products [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	946	859	949
Cost of services [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	512	547	457
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	18,497	17,771	18,682
Sales and marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	26,175	27,579	24,283
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 19,213	$ 20,229	$ 22,698