Other Financial Information - Other Income, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017
Other Financial Information [Abstract]
Gain on equity investments	$ 23.8	$ 0.0	$ 0.0
Net foreign currency exchange gain	4.2	2.6	3.0
Other	0.3	1.6	(0.6)
Total other income, net	$ 28.3	$ 4.2	$ 2.4