Cover - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2021	Jan. 31, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K/A
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-8729
Entity Registrant Name	UNISYS CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	38-0387840
Entity Address, Address Line One	801 Lakeview Drive
Entity Address, Address Line Two	Suite 100
Entity Address, City or Town	Blue Bell
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19422
City Area Code	215
Local Phone Number	986-4011
Title of 12(b) Security	Common Stock, par value $.01
Trading Symbol	UIS
Security Exchange Name	NYSE
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			$ 1.7
Entity Common Stock, Shares Outstanding		67,232,146
Documents Incorporated by Reference	Portions of Unisys Corporation’s Definitive Proxy Statement for the 2022 Annual Meeting of Stockholders are incorporated by reference into Part III hereof.
Amendment Flag	true
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0000746838
Amendment Description	EXPLANATORY NOTE Unisys Corporation is filing this Amendment No. 1 on Form 10-K/A (this amendment) to its Annual Report on Form 10-K for the year ended December 31, 2021, originally filed with the Securities and Exchange Commission (SEC) on February 22, 2022 (the original filing) to address management’s re-evaluation of disclosure controls and procedures and to reflect the identification of material weaknesses in the company’s disclosure controls and procedures and internal control over financial reporting. The material weaknesses did not result in any change to the company’s consolidated financial statements as set forth in the original filing. This amendment is limited in scope to make the following changes to the original filing:     •   To amend Part II - Item 9A. Controls and Procedures related to the effectiveness of our disclosure controls and procedures.     •   To amend Part I - Item 1A. Risk Factors to add an additional risk factor regarding the potential adverse impact that the failure to remediate the material weaknesses could have on our timely and accurate reporting of financial results and to amend a risk factor in the original filing regarding the potential adverse impacts of cybersecurity incidents and vulnerabilities.     •   To amend Part II - Item 8. Financial Statements and Supplementary Data to restate (i) Management’s Report on Internal Control Over Financial Reporting, and (ii) the Report of Independent Registered Public Accounting Firm, on the company’s internal control over financial reporting as of December 31, 2021.     •   To amend Part IV - Item 15. Exhibits and Financial Statement Schedules to include currently dated (i) auditor consents, which are filed herewith as Exhibits 23.1 and 23.2 and (ii) certifications from the company’s Principal Executive Officer and Principal Financial Officer as required by Sections 302 and 906 of the Sarbanes Oxley Act of 2002, which certifications are filed herewith as Exhibits 31.1, 31.2, 32.1 and 32.2. This amendment has not been updated or amended to give effect to any subsequent events beyond those that existed as of the original filing date and should thus be read in conjunction with the original filing and any of the company’s other filings with the SEC subsequent to the original filing, together with any amendments to those filings. Other than the filing of the information identified above, this amendment does not modify or update the disclosure in the original filing in any way.