Income Taxes (Schedule of Unrecognized Tax Benefit Activity) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 30, 2016	Dec. 29, 2017	Sep. 30, 2016	Sep. 25, 2015
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance at beginning of period	$ 114.8	$ 118.7	$ 89.2	$ 82.0
Additions related to current year tax positions	5.0	79.9	63.8	4.5
Additions related to prior period tax positions	0.0	0.3	10.8	19.9
Reductions related to prior period tax positions	(1.1)	(13.6)	(37.8)	(7.7)
Unrecognized Tax Benefits, Decrease Resulting from disposal of business	0.0	0.0	(6.6)	0.0
Settlements	0.0	0.0	(2.6)	(7.8)
Lapse of statute of limitations	0.0	(2.8)	(2.0)	(1.7)
Balance at end of period	$ 118.7	$ 182.5	$ 114.8	$ 89.2