Income Taxes (Reconciliation Of Federal Statutory Tax Rate To Our Effective Tax Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Federal statutory rate	21.00%	24.60%	35.00%
State income taxes, net of federal effect	0.20%	0.70%	0.70%
Stock-based compensation expense rate			1.40%
Stock-based compensation expense rate	(2.80%)	(5.20%)
Research and development tax credits	(3.00%)	(4.50%)	(3.70%)
Tax exempt interest	0.00%	(0.10%)	(0.10%)
U.S. manufacturing tax incentives	0.00%	(0.20%)	(0.80%)
Foreign rate differential	(2.60%)	(5.20%)	(22.90%)
Audit settlements	0.00%	0.00%	(0.60%)
Tax Act	(7.70%)	53.30%	0.00%
Change in Valuation Allowance	1.50%	8.30%	0.00%
Other	2.90%	6.80%	9.80%
Effective tax rate	9.50%	78.50%	18.80%
Unrecognized Tax Benefits	$ 108,539	$ 102,009	$ 98,665	$ 75,168
Unrecognized tax benefits if recognized, would affect our effective tax rate	$ 72,800