Borrowings and Credit Arrangements - Interest Expense Credit Agreement (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 29, 2018	Sep. 30, 2017
2018 Credit Agreement
Line of Credit Facility [Line Items]
Interest expense	$ 46.6
Non-cash interest expense	$ 2.5
Weighted average interest rate	2.25%
Interest rate at end of period	1.40%
2017 Credit Agreement
Line of Credit Facility [Line Items]
Interest expense		$ 67.0
Non-cash interest expense		$ 2.6
Weighted average interest rate		3.79%
Interest rate at end of period		3.43%
Prior Credit Agreement
Line of Credit Facility [Line Items]
Interest expense			$ 60.8
Non-cash interest expense			$ 2.6
Weighted average interest rate			3.23%
Interest rate at end of period				3.74%