GOODWILL AND INTANGIBLE ASSETS - Activity of Goodwill by Reportable Operating Segment (Detail) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Jun. 28, 2019	Dec. 28, 2018	Jun. 29, 2018	Jun. 28, 2019
Goodwill [Roll Forward]
Balance, beginning	[1]		$ 293.6		$ 293.6
Business combinations					326.9
Impairment charges				$ (50.5)
Measurement period adjustments to business combinations in prior year		$ 2.6	(4.7)		(2.1)
Foreign currency translation adjustments					(1.0)
Balance, ending		566.9			566.9
Oncology Systems
Goodwill [Roll Forward]
Balance, beginning			242.1		242.1
Business combinations					204.2
Measurement period adjustments to business combinations in prior year					(2.1)
Balance, ending		444.2			444.2
Proton Solutions
Goodwill [Roll Forward]
Balance, beginning			$ 51.5		51.5
Impairment charges				(50.5)
Foreign currency translation adjustments					(1.0)
Balance, ending		0.0			0.0
Other
Goodwill [Roll Forward]
Business combinations					122.7
Balance, ending		$ 122.7		$ 0.0	$ 122.7

[1] The condensed consolidated balance sheet as of September 28, 2018, 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.