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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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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.

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

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Intangible Assets and Goodwill - Goodwill by Reporting Segment (Details) $ in Millions	12 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2021 reporting_unit	Mar. 31, 2021 unit	Mar. 31, 2020 USD ($)
Goodwill [Roll Forward]
Goodwill, Beginning Balance	$ 6,664.8
Goodwill, Ending Balance	6,670.6			$ 6,664.8
Number of reporting units		2	2
Semiconductor Products Reporting Unit
Goodwill [Roll Forward]
Goodwill, Beginning Balance	6,645.6			6,644.7
Additions	5.8			0.9
Goodwill, Ending Balance	6,651.4			6,645.6
Technology Licensing Reporting Unit
Goodwill [Roll Forward]
Goodwill, Beginning Balance	19.2			19.2
Additions	0.0			0.0
Goodwill, Ending Balance	$ 19.2			$ 19.2