Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

v3.8.0.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2018
Apr. 20, 2018
Document and Entity Information [Abstract]    
Entity Registrant Name CLEVELAND-CLIFFS INC.  
Entity Central Index Key 0000764065  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Document Type 10-Q  
Document Period End Date Mar. 31, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   297,733,061
Trading Symbol clf  
Entity Well-known Seasoned Issuer Yes  
Entity Voluntary Filers No  
Entity Current Reporting Status Yes