Cover
| Cover | Feb. 16, 2021 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Feb. 16, 2021 |
| Entity Registrant Name | United States Steel Corp |
| Entity Central Index Key | 0001163302 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-16811 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| New York Stock Exchange | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | X |
| Security Exchange Name | NYSE |
| Chicago Stock Exchange | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | X |
| Security Exchange Name | CHX |