SEGMENT INFORMATION - Operating Results Information for Each Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 709.1	$ 632.8	$ 2,117.5	$ 1,897.5
Operating Earnings (Loss)	91.5	88.5	307.2	196.0
Oncology Systems
Segment Reporting Information [Line Items]
Revenues	667.2	564.4	2,014.6	1,767.5
Varian Particle Therapy
Segment Reporting Information [Line Items]
Revenues	41.9	68.4	102.9	130.0
Unallocated corporate
Segment Reporting Information [Line Items]
Operating Earnings (Loss)	(24.0)	(3.4)	(56.9)	(64.8)
Operating Segments
Segment Reporting Information [Line Items]
Operating Earnings (Loss)	115.5	91.9	364.1	260.8
Operating Segments | Oncology Systems
Segment Reporting Information [Line Items]
Revenues	667.2	564.4	2,014.6	1,767.5
Operating Earnings (Loss)	125.6	104.3	406.9	343.3
Operating Segments | Varian Particle Therapy
Segment Reporting Information [Line Items]
Revenues	41.9	68.4	102.9	130.0
Operating Earnings (Loss)	$ (10.1)	$ (12.4)	$ (42.8)	$ (82.5)