Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 30, 2016	Dec. 29, 2017	Sep. 30, 2016	Sep. 25, 2015
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 4.0	$ 4.0	$ 3.6	$ 2.2
Charged to Income	0.1	0.6	0.3	1.2
Additions and Other	0.0	0.0	0.0	0.0
Deductions	(0.1)	(0.7)	(0.1)	0.2
Balance at End of Period	4.0	3.9	4.0	3.6
Sales reserve accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	378.0	391.3	396.4	402.2
Charged to Income	515.3	2,008.5	2,030.8	2,177.4
Additions and Other	0.0	0.0	0.0	1.3
Deductions	(502.0)	(2,023.2)	(2,049.2)	(2,184.5)
Balance at End of Period	391.3	376.6	378.0	396.4
Tax valuation allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	564.9	1,398.3	233.0	76.9
Charged to Income	833.4	804.6	315.7	155.4
Additions and Other	0.0	4.0	15.8	0.2
Deductions	0.0	(61.0)	0.4	0.5
Balance at End of Period	$ 1,398.3	$ 2,267.9	$ 564.9	$ 233.0