Annual report pursuant to Section 13 and 15(d)

RELATED PARTIES (Summary Of Related Party Transactions Table Disclosure) (Details)

v2.4.1.9
RELATED PARTIES (Summary Of Related Party Transactions Table Disclosure) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Related Party Transactions [Abstract]      
Product revenues from related parties $ 1,378.7us-gaap_RevenueFromRelatedParties $ 1,664.8us-gaap_RevenueFromRelatedParties $ 1,660.8us-gaap_RevenueFromRelatedParties
Product $ 4,230.8us-gaap_SalesRevenueGoodsNet $ 5,346.6us-gaap_SalesRevenueGoodsNet $ 5,520.9us-gaap_SalesRevenueGoodsNet
Related party product revenue as a percent of total product revenue 32.60%clf_PercentageOfRelatedPartyRevenue 31.10%clf_PercentageOfRelatedPartyRevenue 30.10%clf_PercentageOfRelatedPartyRevenue