Goodwill and Intangible Assets - Activity of Goodwill by Reportable Operating Segment (Detail) - USD ($) $ in Millions	12 Months Ended
Sep. 28, 2018	Sep. 29, 2017
Goodwill [Roll Forward]
Balance, beginning	$ 222.6	$ 220.0
Business combinations	72.1
Foreign currency translation adjustments	(1.1)	2.6
Balance, ending	293.6	222.6
Oncology Systems
Goodwill [Roll Forward]
Balance, beginning	170.2	170.2
Business combinations	72.1
Foreign currency translation adjustments	(0.2)	0.0
Balance, ending	242.1	170.2
Proton Solutions
Goodwill [Roll Forward]
Balance, beginning	52.4	49.8
Business combinations	0.0
Foreign currency translation adjustments	(0.9)	2.6
Balance, ending	$ 51.5	$ 52.4

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://fasb.org/us-gaap/role/ref/legacyRef
-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

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- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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