Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Dec. 27, 2019	Dec. 28, 2018
Statement of Cash Flows [Abstract]
Net income	$ 257.1	$ 284.9
Adjustments to reconcile net income to net cash provided by operating activities:
Share-based compensation	33.6	20.8
Depreciation	79.8	77.5
Amortization of intangible assets, including inventory step-up	11.4	15.5
Deferred income taxes	0.9	1.8
Other, net	0.0	1.0
Changes in assets and liabilities:
Receivables, net	38.5	131.4
Inventory	7.9	(5.0)
Accounts payable	(6.7)	(22.2)
Other current and long-term assets and liabilities	(24.1)	43.3
Net Cash Provided by (Used in) Operating Activities	398.4	549.0
Cash flows from investing activities:
Capital expenditures	(111.2)	(129.5)
Payments to Acquire Marketable Securities	(131.5)	(2.2)
Maturity of investments	62.2	303.2
Net Cash Provided by (Used in) Investing Activities	(180.5)	171.5
Cash flows from financing activities:
Repurchase of common stock - payroll tax withholdings on equity awards	(26.6)	(19.4)
Repurchase of common stock - stock repurchase program	(74.2)	(284.0)
Dividends paid	(75.1)	(67.1)
Net proceeds from exercise of stock options	34.9	2.4
Net Cash Provided by (Used in) Financing Activities	(141.0)	(368.1)
Net increase in cash and cash equivalents	76.9	352.4
Cash and cash equivalents at beginning of period	851.3	733.3
Cash and cash equivalents at end of period	928.2	1,085.7
Supplemental cash flow disclosures:
Income taxes paid	26.1	1.6
Capital Expenditures Incurred but Not yet Paid	$ 70.1	$ 56.7