Goodwill by Reporting Segment (Details) $ in Millions	3 Months Ended
Jun. 30, 2018 USD ($)	Jun. 30, 2017 unit
Goodwill By Reporting Segment [Line Items]
Number of reporting units \| unit		2
Goodwill [Roll Forward]
Goodwill	$ 2,299.0
Goodwill	7,273.2
Semiconductor products
Goodwill [Roll Forward]
Goodwill	2,279.8
Goodwill	7,254.0
Technology licensing
Goodwill [Roll Forward]
Goodwill	19.2
Goodwill	19.2
Microsemi Corporation \| Semiconductor products
Goodwill [Roll Forward]
Additions due to the acquisition of Microsemi	4,974.2
Microsemi Corporation \| Technology licensing
Goodwill [Roll Forward]
Additions due to the acquisition of Microsemi	$ 0.0

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

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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

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- Definition

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+ References

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- Definition

Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment.

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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