Other Financial Information - Components of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Millions	Sep. 27, 2019	Sep. 28, 2018
Other Financial Information [Abstract]
Prepaid income taxes	$ 51.1	$ 48.1
Prepaid sales taxes	21.0	17.5
Prepaid compensation	13.7	14.2
Advance payments to suppliers	15.3	16.6
Available-for-sale securities	0.0	39.4
RPTC secured debt	0.0	24.9
Other current receivables	47.2	24.1
Other prepaid expenses	57.9	48.5
Total prepaid expenses and other current assets	$ 206.2	$ 233.3