Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 27, 2020	Sep. 29, 2019	Sep. 30, 2018
Debt Securities, Available-for-sale [Abstract]
Proceeds from sale of available-for-sale securities	$ 177.4	$ 291.1	$ 459.0
Trading Securities [Abstract]
Management Deferred Compensation Plan liability	$ 91.4	$ 92.1
Maximum [Member]
Debt Securities, Available-for-sale [Abstract]
Long-term investments, contractual maturity period	4 years

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements payable within one year (or the operating cycle, if longer). Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 25
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=6409733&loc=d3e19512-108361

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 30
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20028-108363

Name:	us-gaap_DeferredCompensationLiabilityCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant