SEGMENT INFORMATION - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jul. 03, 2020	Jun. 28, 2019	Jul. 03, 2020	Jun. 28, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 694.3	$ 825.8	$ 2,317.7	$ 2,346.2
Products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues	297.6	437.1	1,092.7	1,206.3
Products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenues	396.7	388.7	1,225.0	1,139.9
Americas
Disaggregation of Revenue [Line Items]
Revenues	337.5	401.2	1,127.6	1,122.9
EMEA
Disaggregation of Revenue [Line Items]
Revenues	217.2	271.3	741.0	783.8
APAC
Disaggregation of Revenue [Line Items]
Revenues	139.6	153.3	449.1	439.5
North America
Disaggregation of Revenue [Line Items]
Revenues	324.2	378.7	1,064.9	1,050.8
International
Disaggregation of Revenue [Line Items]
Revenues	370.1	447.1	1,252.8	1,295.4
Hardware
Disaggregation of Revenue [Line Items]
Revenues	264.0	387.9	963.9	1,102.1
Software
Disaggregation of Revenue [Line Items]
Revenues	143.2	155.7	446.7	431.1
Service
Disaggregation of Revenue [Line Items]
Revenues	287.1	282.2	907.1	813.0
Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	687.2	823.8	2,280.0	2,344.2
Operating Segments | Oncology Systems
Disaggregation of Revenue [Line Items]
Revenues	654.5	792.9	2,197.4	2,242.2
Operating Segments | Oncology Systems | Products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues	290.0	433.8	1,053.0	1,203.0
Operating Segments | Oncology Systems | Products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenues	364.5	359.1	1,144.4	1,039.2
Operating Segments | Oncology Systems | Americas
Disaggregation of Revenue [Line Items]
Revenues	318.1	385.6	1,066.7	1,073.5
Operating Segments | Oncology Systems | EMEA
Disaggregation of Revenue [Line Items]
Revenues	204.1	256.4	704.8	736.2
Operating Segments | Oncology Systems | APAC
Disaggregation of Revenue [Line Items]
Revenues	132.3	150.9	425.9	432.5
Operating Segments | Oncology Systems | North America
Disaggregation of Revenue [Line Items]
Revenues	304.8	363.1	1,004.0	1,001.4
Operating Segments | Oncology Systems | International
Disaggregation of Revenue [Line Items]
Revenues	349.7	429.8	1,193.4	1,240.8
Operating Segments | Oncology Systems | Hardware
Disaggregation of Revenue [Line Items]
Revenues	234.3	361.7	870.4	1,014.4
Operating Segments | Oncology Systems | Software
Disaggregation of Revenue [Line Items]
Revenues	142.7	154.4	444.7	429.8
Operating Segments | Oncology Systems | Service
Disaggregation of Revenue [Line Items]
Revenues	277.5	276.8	882.3	798.0
Operating Segments | Proton Solutions
Disaggregation of Revenue [Line Items]
Revenues	32.7	30.9	82.6	102.0
Operating Segments | Proton Solutions | Products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues	0.5	1.3	2.0	1.3
Operating Segments | Proton Solutions | Products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenues	32.2	29.6	80.6	100.7
Operating Segments | Proton Solutions | Americas
Disaggregation of Revenue [Line Items]
Revenues	14.9	14.8	43.2	48.6
Operating Segments | Proton Solutions | EMEA
Disaggregation of Revenue [Line Items]
Revenues	12.7	14.9	32.8	47.6
Operating Segments | Proton Solutions | APAC
Disaggregation of Revenue [Line Items]
Revenues	5.1	1.2	6.6	5.8
Operating Segments | Proton Solutions | North America
Disaggregation of Revenue [Line Items]
Revenues	14.9	14.8	43.2	48.6
Operating Segments | Proton Solutions | International
Disaggregation of Revenue [Line Items]
Revenues	17.8	16.1	39.4	53.4
Operating Segments | Proton Solutions | Hardware
Disaggregation of Revenue [Line Items]
Revenues	22.6	24.2	55.8	85.7
Operating Segments | Proton Solutions | Software
Disaggregation of Revenue [Line Items]
Revenues	0.5	1.3	2.0	1.3
Operating Segments | Proton Solutions | Service
Disaggregation of Revenue [Line Items]
Revenues	9.6	5.4	24.8	15.0
Other
Disaggregation of Revenue [Line Items]
Revenues	7.1	2.0	37.7	2.0
Other | Products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues	7.1	2.0	37.7	2.0
Other | Americas
Disaggregation of Revenue [Line Items]
Revenues	4.5	0.8	17.7	0.8
Other | EMEA
Disaggregation of Revenue [Line Items]
Revenues	0.4	0.0	3.4	0.0
Other | APAC
Disaggregation of Revenue [Line Items]
Revenues	2.2	1.2	16.6	1.2
Other | North America
Disaggregation of Revenue [Line Items]
Revenues	4.5	0.8	17.7	0.8
Other | International
Disaggregation of Revenue [Line Items]
Revenues	2.6	1.2	20.0	1.2
Other | Hardware
Disaggregation of Revenue [Line Items]
Revenues	$ 7.1	$ 2.0	$ 37.7	$ 2.0