SEGMENT INFORMATION - Operating Results Information for Each Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 29, 2019	Mar. 30, 2018	Mar. 29, 2019	Mar. 30, 2018
Segment Reporting Information [Line Items]
Revenues	$ 779.4	$ 729.9	$ 1,520.4	$ 1,408.4
Earnings before taxes	109.8	109.1	221.5	230.7
Interest income, net	3.0	1.3	5.7	2.4
Other income (expense), net	0.2	(14.8)	23.2	(15.0)
Earnings before taxes	113.0	95.6	250.4	218.1
Oncology Systems
Segment Reporting Information [Line Items]
Revenues	746.8	698.0	1,449.3	1,347.4
Proton Solutions
Segment Reporting Information [Line Items]
Revenues	32.6	31.9	71.1	61.0
Unallocated corporate
Segment Reporting Information [Line Items]
Earnings before taxes	(1.9)	(16.5)	(5.5)	(17.9)
Operating Segments
Segment Reporting Information [Line Items]
Earnings before taxes	111.7	125.6	227.0	248.6
Operating Segments \| Oncology Systems
Segment Reporting Information [Line Items]
Revenues	746.8	698.0	1,449.3	1,347.4
Earnings before taxes	131.7	143.1	255.8	281.3
Operating Segments \| Proton Solutions
Segment Reporting Information [Line Items]
Revenues	32.6	31.9	71.1	61.0
Earnings before taxes	$ (20.0)	$ (17.5)	$ (28.8)	$ (32.7)

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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