Consolidated and Combined Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended									12 Months Ended
	Dec. 29, 2017	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 30, 2016	Sep. 30, 2016	Jun. 24, 2016	Mar. 25, 2016	Dec. 25, 2015	Dec. 29, 2017	Sep. 30, 2016	Sep. 25, 2015
Net income (loss)	$ 1,608.7	$ 63.7	$ 62.8	$ 399.2	$ (153.2)	$ 115.0	$ 199.3	$ 118.3	$ 211.1	$ 2,134.4	$ 643.7	$ 324.7
Other comprehensive income (loss), net of tax
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax					0.0					1.5	0.0	0.0
Currency translation adjustments					(21.1)					11.3	(58.6)	(70.8)
Unrecognized gain on derivatives, net of tax expense of $0.3, $0.2, $0.2 and $-					0.2					1.0	0.5	0.4
Unrecognized gain (loss) on benefit plans, net of tax expense (benefit) of $30.8, ($15.0), ($2.1) and ($19.3)					34.0					45.8	(28.4)	5.6
Total other comprehensive income (loss), net of tax					13.1					59.6	(86.5)	(64.8)
Comprehensive income (loss)					$ (140.1)					$ 2,194.0	$ 557.2	$ 259.9