Income Taxes (Reconciliation Of Federal Statutory Tax Rate To Our Effective Tax Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 29, 2017	Sep. 30, 2016	Sep. 25, 2015	Sep. 26, 2014
Income Tax Disclosure [Abstract]
Federal statutory rate	35.00%	35.00%	35.00%
State income taxes, net of federal effect	0.70%	0.70%	0.70%
Stock-based compensation expense rate	1.40%	1.50%	1.70%
Research and development tax credits	(3.70%)	(5.20%)	(3.00%)
Tax exempt interest	(0.10%)	(0.10%)	(0.20%)
U.S. manufacturing tax incentives	(0.80%)	(1.10%)	(0.30%)
Foreign rate differential	(11.70%)	(9.50%)	(9.10%)
Audit settlements	(0.60%)	(2.30%)	(0.00%)
Other	0.90%	2.00%	0.60%
Effective tax rate	21.10%	21.00%	25.40%
Unrecognized Tax Benefits	$ 98,665	$ 75,168	$ 65,161	$ 31,351
Unrecognized tax benefits if recognized, would affect our effective tax rate	$ 85,000