Income Taxes (Summary Of Tax Effects Of The Temporary Differences Between Carrying Amounts And Amounts Used For Tax) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 28, 2018	Sep. 29, 2017
Income Tax Disclosure [Abstract]
Document Period End Date	Sep. 28, 2018
Investments	$ 2,215	$ 2,327
Inventories	4,070	6,821
Net operating loss	2,174	2,806
Accrued expenses	12,573	19,732
Stock-based compensation	15,601	26,970
Revenue recognition	33,464	53,843
Depreciation and amortization	16,078	52,876
Research and development credits	21,302	15,504
Foreign tax credits	9,345	10,140
Deferred Tax Assets, Unrealized Currency Losses	0	625
Other	3,335	6,696
Total gross deferred income tax assets	120,157	198,340
Less: valuation allowance	(16,256)	0
Total deferred income tax assets	103,901	198,340
Intangibles	(2,831)	(2,277)
International earnings	0	(4,855)
Unrealized gain on investments	0	(293)
Deferred income tax assets, net	101,070	$ 190,915
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration	8,600
Deferred Tax Assets, Tax Credit Carryforwards, Research	$ 4,900