Marketable Securities (Details) - USD ($) $ in Millions	Apr. 02, 2021	Oct. 02, 2020
Other Current Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	$ 359.7	$ 408.1
Other Noncurrent Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	4.0	5.2
US Treasury and Government [Member] | Other Current Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	105.0	129.4
US Treasury and Government [Member] | Other Noncurrent Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	0.0	5.0
Corporate Debt Securities [Member] | Other Current Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	251.8	276.8
Corporate Debt Securities [Member] | Other Noncurrent Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	2.2	0.0
US States and Political Subdivisions Debt Securities [Member] | Other Current Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	2.9	1.9
US States and Political Subdivisions Debt Securities [Member] | Other Noncurrent Assets [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities	$ 1.8	$ 0.2