Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 27, 2020	Mar. 29, 2019	Mar. 27, 2020	Mar. 29, 2019	Sep. 27, 2019
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, gross	$ 111,500		$ 111,500		$ 108,500
Unrecognized tax benefits if recognized, would affect our effective tax rate	$ 73,100		$ 73,100		$ 72,800
Effective tax rate (as a percent)	20.00%	33.10%	16.90%	6.70%
Provision (benefit) for income taxes	$ 22,105	$ 36,427	$ 27,968	$ 12,323
Federal tax rate	21.00%