SEGMENT INFORMATION - Operating Results Information for Each Reportable Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jul. 03, 2020	Jun. 28, 2019	Jul. 03, 2020	Jun. 28, 2019
Segment Reporting Information [Line Items]
Revenues	$ 694.3	$ 825.8	$ 2,317.7	$ 2,346.2
Earnings before taxes	59.9	53.9	224.8	275.4
Interest income (expense), net	(0.2)	1.9	(3.1)	7.6
Other income, net	25.1	4.2	28.6	27.4
Earnings before taxes	84.8	60.0	250.3	310.4
Operating Segments
Segment Reporting Information [Line Items]
Revenues	687.2	823.8	2,280.0	2,344.2
Earnings before taxes	93.2	86.6	311.9	313.6
Operating Segments | Oncology Systems
Segment Reporting Information [Line Items]
Revenues	654.5	792.9	2,197.4	2,242.2
Earnings before taxes	101.1	148.7	348.4	404.5
Operating Segments | Proton Solutions
Segment Reporting Information [Line Items]
Revenues	32.7	30.9	82.6	102.0
Earnings before taxes	(7.9)	(62.1)	(36.5)	(90.9)
Other
Segment Reporting Information [Line Items]
Revenues	7.1	2.0	37.7	2.0
Earnings before taxes	(5.4)	(1.7)	(4.9)	(1.7)
Unallocated corporate
Segment Reporting Information [Line Items]
Earnings before taxes	$ (27.9)	$ (31.0)	$ (82.2)	$ (36.5)