Income Taxes (Summary Of Tax Effects Of The Temporary Differences Between Carrying Amounts And Amounts Used For Tax) (Details) - USD ($) $ in Thousands	Sep. 27, 2019	Sep. 28, 2018
Income Tax Disclosure [Abstract]
Investments	$ 2,099	$ 2,215
Inventories	4,041	4,070
Net operating loss	2,050	2,174
Accrued expenses	13,917	12,573
Stock-based compensation	17,189	15,601
Revenue recognition	4,410	7,161
Depreciation and amortization	19,988	16,078
Research and development credits	28,777	21,302
Foreign tax credits	10,777	9,345
Deferred Tax Assets, Unrealized Currency Losses	33,357	0
Other	4,705	3,334
Total gross deferred income tax assets	141,310	93,853
Less: valuation allowance	(24,884)	(16,256)
Total deferred income tax assets	116,426	77,597
Intangibles	(2,351)	(2,831)
Deferred income tax assets, net	114,075	$ 74,766
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration	8,300
Deferred Tax Assets, Tax Credit Carryforwards, Research	$ 8,400