GOODWILL AND INTANGIBLE ASSETS - Activity of Goodwill by Reportable Operating Segment (Detail) $ in Millions	3 Months Ended
Dec. 29, 2017 USD ($)
Goodwill [Roll Forward]
Balance, beginning	$ 222.6
Foreign currency translation adjustments	0.8
Balance, ending	223.4
Oncology Systems
Goodwill [Roll Forward]
Balance, beginning	170.2
Foreign currency translation adjustments	0.0
Balance, ending	170.2
Varian Particle Therapy
Goodwill [Roll Forward]
Balance, beginning	52.4
Foreign currency translation adjustments	0.8
Balance, ending	$ 53.2

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant