Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

v3.7.0.1
Document and Entity Information - shares
6 Months Ended
Jun. 30, 2017
Jul. 24, 2017
Document and Entity Information [Abstract]    
Entity Registrant Name CLIFFS NATURAL RESOURCES 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 Jun. 30, 2017  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   296,506,003
Trading Symbol clf