Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 30, 2017	Sep. 28, 2019	Sep. 29, 2018	Sep. 30, 2017
Federal:
Current		$ 142.9	$ 137.1	$ 701.1
Deferred		(189.9)	(461.9)	(276.9)
Federal, Total		(47.0)	(324.8)	424.2
State:
Current		22.1	11.0	53.1
Deferred		(41.0)	(11.3)	(15.9)
State, Total		(18.9)	(0.3)	37.2
Foreign:
Current		16.5	21.9	13.9
Deferred		(4.7)	(4.1)	(0.3)
Foreign, Total		11.8	17.8	13.6
Provision for income taxes	$ 329.2	$ (54.1)	$ (307.3)	$ 475.0