GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 03, 2020	Mar. 29, 2019	Apr. 03, 2020	Mar. 29, 2019	Sep. 27, 2019
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 137.6		$ 137.6		$ 137.5
Accumulated amortization	(62.9)		(62.9)		(54.0)
Total intangible assets with finite lives, net carrying amount	74.7		74.7		83.5
In-process research and development with indefinite lives	2.8		2.8		2.8
Total intangible assets	140.4		140.4		140.3
Total intangible assets, net	77.5		77.5		86.3
Amortization of intangible assets	4.4	$ 3.6	8.9	$ 7.3
Acquired existing technology
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	74.1		74.1		74.1
Accumulated amortization	(33.1)		(33.1)		(28.4)
Total intangible assets with finite lives, net carrying amount	41.0		41.0		45.7
Patents, licenses and other
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	12.8		12.8		12.7
Accumulated amortization	(9.1)		(9.1)		(8.4)
Total intangible assets with finite lives, net carrying amount	3.7		3.7		4.3
Customer contracts and supplier relationship
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	50.7		50.7		50.7
Accumulated amortization	(20.7)		(20.7)		(17.2)
Total intangible assets with finite lives, net carrying amount	$ 30.0		$ 30.0		$ 33.5