Cleveland-Cliffs Inc. Annual report pursuant to Section 13 and 15(d)

PENSIONS AND OTHER POSTRETIREMENT BENEFITS - Narrative (Details)	Jan. 01, 2023 USD ($)	Dec. 31, 2022 USD ($)	Nov. 01, 2022 USD ($)	Oct. 31, 2022 USD ($)	Oct. 12, 2022 location employee	Sep. 30, 2022 USD ($) employee
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Term of labor agreement					4 years	47 months
Number of employees covered by labor agreement \| employee					12,000	2,000
Number of locations covered by labor agreement \| location					13
Service multiplier						$ 115
Contribution per eligible hour			$ 4.00	$ 0.50
Forecast
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service multiplier	$ 126
Fixed income \| Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan asset investment		$ 1,200,000,000
Externally Managed Assets \| Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan asset investment		$ 2,900,000,000