Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	Sep. 30, 2016	Sep. 25, 2015
Tax Credit Carryforward [Line Items]
Net operating loss carryovers for California tax purposes	$ 5,800
Effective tax rate	60.70%	21.10%	21.00%
Unrecognized tax benefits, gross	$ 102,009	$ 98,665	$ 75,168	$ 65,161
Unrecognized tax benefits if recognized, would affect our effective tax rate	96,900
Estimated decrease in unrecognized tax benefits due to lapse in statute of limitations	1,900
Increase in interest expense for current tax provision	3,000	$ 1,800
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration	8,600
Deferred Tax Assets, Tax Credit Carryforwards, Research	4,900
Foreign Tax Credit Carryforward [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforward	6,900
California Research Tax Credit Carryforward [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforward	24,100
Research Tax Credit Carryforward [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforward	$ 1,800