Annual report pursuant to Section 13 and 15(d)

INVENTORIES (Schedule Of Inventories) (Details)

v2.4.1.9
INVENTORIES (Schedule Of Inventories) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Inventory, Net [Abstract]    
Finished Goods $ 207.9us-gaap_InventoryFinishedGoodsNetOfReserves $ 256.5us-gaap_InventoryFinishedGoodsNetOfReserves
Work-in Process 118.8us-gaap_InventoryWorkInProcessNetOfReserves 134.9us-gaap_InventoryWorkInProcessNetOfReserves
Total Inventory 326.7us-gaap_InventoryNet 391.4us-gaap_InventoryNet
U.S. Iron Ore [Member]    
Inventory, Net [Abstract]    
Finished Goods 132.1us-gaap_InventoryFinishedGoodsNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
92.1us-gaap_InventoryFinishedGoodsNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Work-in Process 13.5us-gaap_InventoryWorkInProcessNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
13.0us-gaap_InventoryWorkInProcessNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Total Inventory 145.6us-gaap_InventoryNet
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
105.1us-gaap_InventoryNet
/ us-gaap_StatementBusinessSegmentsAxis
= clf_USIronOreMember
Eastern Canadian Iron Ore [Member]    
Inventory, Net [Abstract]    
Finished Goods 16.3us-gaap_InventoryFinishedGoodsNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
65.3us-gaap_InventoryFinishedGoodsNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
Work-in Process 0us-gaap_InventoryWorkInProcessNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
48.1us-gaap_InventoryWorkInProcessNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
Total Inventory 16.3us-gaap_InventoryNet
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
113.4us-gaap_InventoryNet
/ us-gaap_StatementBusinessSegmentsAxis
= clf_EasternCanadianIronOreMember
Asia Pacific Iron Ore [Member]    
Inventory, Net [Abstract]    
Finished Goods 26.4us-gaap_InventoryFinishedGoodsNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
39.7us-gaap_InventoryFinishedGoodsNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
Work-in Process 88.1us-gaap_InventoryWorkInProcessNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
50.6us-gaap_InventoryWorkInProcessNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
Total Inventory 114.5us-gaap_InventoryNet
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
90.3us-gaap_InventoryNet
/ us-gaap_StatementBusinessSegmentsAxis
= clf_AsiaPacificIronOreMember
North American Coal [Member]    
Inventory, Net [Abstract]    
Finished Goods 33.1us-gaap_InventoryFinishedGoodsNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_NorthAmericanCoalMember
59.4us-gaap_InventoryFinishedGoodsNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_NorthAmericanCoalMember
Work-in Process 17.2us-gaap_InventoryWorkInProcessNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_NorthAmericanCoalMember
23.2us-gaap_InventoryWorkInProcessNetOfReserves
/ us-gaap_StatementBusinessSegmentsAxis
= clf_NorthAmericanCoalMember
Total Inventory $ 50.3us-gaap_InventoryNet
/ us-gaap_StatementBusinessSegmentsAxis
= clf_NorthAmericanCoalMember
$ 82.6us-gaap_InventoryNet
/ us-gaap_StatementBusinessSegmentsAxis
= clf_NorthAmericanCoalMember