Intangible Assets and Goodwill - Goodwill by Reporting Segment (Details) $ in Millions	12 Months Ended
Mar. 31, 2020 USD ($) unit	Sep. 30, 2020 USD ($)
Goodwill By Reporting Segment [Line Items]
Goodwill	$ 6,664.8	$ 6,664.8
Number of reporting units \| unit	2
Semiconductor Products Reporting Unit
Goodwill By Reporting Segment [Line Items]
Goodwill		6,645.6
Technology Licensing Reporting Unit
Goodwill By Reporting Segment [Line Items]
Goodwill		$ 19.2

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

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant