GOODWILL AND INTANGIBLE ASSETS - Activity of Goodwill by Reportable Operating Segment (Detail) $ in Millions	9 Months Ended
	Jun. 30, 2017 USD ($)
Goodwill [Roll Forward]
Balance, beginning	$ 220.0	[1]
Foreign currency translation adjustments	0.8
Balance, ending	220.8
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	49.8
Foreign currency translation adjustments	0.8
Balance, ending	$ 50.6

[1] The condensed consolidated balance sheet as of September 30, 2016 was derived from audited financial statements as of that date, but does not include all disclosures required by accounting principles generally accepted in the United States of America.