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

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Summary Of Mine Closure Obligations) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Environmental	$ 5.5	$ 8.4
Mine Reclamation and Closing Liability, current and noncurrent	255.7	312.6
Total environmental and mine closure obligations	261.2	321.0
Less current portion	5.2	11.3
Long term environmental and mine closure obligations	256.0	309.7
U.S. Iron Ore [Member] \| Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	120.9	152.2
Eastern Canadian Iron Ore [Member] \| Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	56.5	78.2
Asia Pacific Iron Ore [Member] \| Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	21.5	25.5
North American Coal [Member] \| Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	33.9	34.7
LTV Steel Mining Company [Member] \| Previously Owned Or Operating Facilities [Member]
Loss Contingencies [Line Items]
Mine Reclamation and Closing Liability, current and noncurrent	$ 22.9	$ 22.0