Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2021	Feb. 07, 2022	Jun. 30, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Document Transition Report	false
Entity File Number	1-16811
Entity Registrant Name	United States Steel Corp
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	25-1897152
Entity Address, Address Line One	600 Grant Street
Entity Address, City or Town	Pittsburgh
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15219-2800
City Area Code	412
Local Phone Number	433-1121
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
Smaller Reporting Company	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 6.5
Entity Common Stock, Shares Outstanding		260,930,638
Documents Incorporated by Reference	Portions of the Proxy Statement for the 2022 Annual Meeting of Stockholders are incorporated into Part III.
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0001163302
Current Fiscal Year End Date	--12-31
New York Stock Exchange
Entity Information [Line Items]
Title of 12(b) Security	United States Steel Corporation Common Stock, par value $1.00
Trading Symbol	X
Security Exchange Name	NYSE
Chicago Stock Exchange
Entity Information [Line Items]
Title of 12(b) Security	United States Steel Corporation Common Stock, par value $1.00
Trading Symbol	X
Security Exchange Name	CHX