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Cover Page - USD ($)	12 Months Ended
Cover Page - USD ($)	Dec. 31, 2020	Feb. 10, 2021	Jul. 03, 2020
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-39317
Entity Registrant Name	ON SEMICONDUCTOR CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-3840979
Entity Address, Address Line One	5005 E. McDowell Road
Entity Address, City or Town	Phoenix
Entity Address, State or Province	AZ
Entity Address, Postal Zip Code	85008
City Area Code	602
Local Phone Number	244-6600
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 7,783,044,394
Entity Common Stock, Shares Outstanding		411,881,071
Documents Incorporated by Reference	Documents Incorporated by Reference Portions of the registrant's Definitive Proxy Statement relating to its 2021 Annual Meeting of Stockholders, which is expected to be filed pursuant to Regulation 14A within 120 days after the registrant's fiscal year ended December 31, 2020, are incorporated by reference into Part III of this Form 10-K.
Entity Central Index Key	0001097864
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020
Amendment Flag	false
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	ON
Security Exchange Name	NASDAQ
Series B Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	Preferred Stock, Series B Junior Participating, Purchase Rights
Security Exchange Name	NASDAQ