INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 29, 2019	Mar. 30, 2018	Mar. 29, 2019	Mar. 30, 2018	Sep. 28, 2018
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ (45.8)		$ (45.8)		$ (40.6)
Total intangible assets with finite lives	61.8		61.8		69.8
In-process research and development with indefinite lives	4.0		4.0		4.0
Total intangible assets	65.8		65.8		73.8
Amortization of intangible assets	3.6	$ 4.2	7.3	$ 8.4
Impairment of intangible assets	0.8		0.8	$ 0.0
Acquired existing technology
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	55.6		55.6		57.9
Patents, licenses and other
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	9.9		9.9		9.9
Customer contracts and supplier relationship
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 42.1		$ 42.1		$ 42.6