Annual report pursuant to Section 13 and 15(d)

EARNINGS PER SHARE (Earnings Per Share Computation) (Details)

v2.4.1.9
EARNINGS PER SHARE (Earnings Per Share Computation) (Details) (USD $)
In Millions, except Share data, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount 25,200,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount             12,900,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount 25,200,000us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount    
Income (Loss) from Continuing Operations Attributable to Parent $ (1,285.1)us-gaap_IncomeLossFromContinuingOperations $ (5,879.6)us-gaap_IncomeLossFromContinuingOperations $ 10.9us-gaap_IncomeLossFromContinuingOperations $ (70.3)us-gaap_IncomeLossFromContinuingOperations $ 43.3us-gaap_IncomeLossFromContinuingOperations $ 115.2us-gaap_IncomeLossFromContinuingOperations $ 146.0us-gaap_IncomeLossFromContinuingOperations $ 107.0us-gaap_IncomeLossFromContinuingOperations $ (7,224.2)us-gaap_IncomeLossFromContinuingOperations $ 411.5us-gaap_IncomeLossFromContinuingOperations $ (935.3)us-gaap_IncomeLossFromContinuingOperations
Income (Loss) and Gain on Sale from Discontinued Operations, net of tax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax     0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 2.0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 2.0us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 35.9us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS SHAREHOLDERS (1,285.1)us-gaap_NetIncomeLoss (5,879.6)us-gaap_NetIncomeLoss 10.9us-gaap_NetIncomeLoss (70.3)us-gaap_NetIncomeLoss 43.3us-gaap_NetIncomeLoss 117.2us-gaap_NetIncomeLoss 146.0us-gaap_NetIncomeLoss 107.0us-gaap_NetIncomeLoss (7,224.2)us-gaap_NetIncomeLoss 413.5us-gaap_NetIncomeLoss (899.4)us-gaap_NetIncomeLoss
PREFERRED STOCK DIVIDENDS (12.8)us-gaap_DividendsPreferredStock (12.8)us-gaap_DividendsPreferredStock (12.8)us-gaap_DividendsPreferredStock (12.8)us-gaap_DividendsPreferredStock         (51.2)us-gaap_DividendsPreferredStock (48.7)us-gaap_DividendsPreferredStock 0us-gaap_DividendsPreferredStock
NET INCOME (LOSS) ATTRIBUTABLE TO CLIFFS COMMON SHAREHOLDERS (1,297.9)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic (5,892.4)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic (1.9)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic (83.1)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic         (7,275.4)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 364.8us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic (899.4)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements                 700,000clf_AntidilutiveIncrementalCommonSharesExcludedandAttributabletoSharebasedPaymentArrangements 0clf_AntidilutiveIncrementalCommonSharesExcludedandAttributabletoSharebasedPaymentArrangements 500,000clf_AntidilutiveIncrementalCommonSharesExcludedandAttributabletoSharebasedPaymentArrangements
Weighted Average Number of Shares:                      
Basic                 153,098,000us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 151,726,000us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 142,351,000us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
Depositary Shares                 0clf_WeightedAverageNumberOfSharesOustandingDepositary 458,000clf_WeightedAverageNumberOfSharesOustandingDepositary 0clf_WeightedAverageNumberOfSharesOustandingDepositary
Employee Stock Plans                 0us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements 22,139,000us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements 0us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements
Diluted                 153,098,000us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 174,323,000us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 142,351,000us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
Earnings (loss) per Common Share Attributable to Cliffs Common Shareholders - Basic:                      
Continuing operations $ (8.48)us-gaap_IncomeLossFromContinuingOperationsPerBasicShare $ (38.49)us-gaap_IncomeLossFromContinuingOperationsPerBasicShare $ (0.01)us-gaap_IncomeLossFromContinuingOperationsPerBasicShare $ (0.54)us-gaap_IncomeLossFromContinuingOperationsPerBasicShare $ 0.20us-gaap_IncomeLossFromContinuingOperationsPerBasicShare $ 0.67us-gaap_IncomeLossFromContinuingOperationsPerBasicShare $ 0.87us-gaap_IncomeLossFromContinuingOperationsPerBasicShare $ 0.66us-gaap_IncomeLossFromContinuingOperationsPerBasicShare $ (47.52)us-gaap_IncomeLossFromContinuingOperationsPerBasicShare $ 2.39us-gaap_IncomeLossFromContinuingOperationsPerBasicShare $ (6.57)us-gaap_IncomeLossFromContinuingOperationsPerBasicShare
Discontinued operations $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare     $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare $ 0.01us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare $ 0.01us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare $ 0.25us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare
Earnings (loss) per Common Share Attributable to Cliffs Common Shareholders - Basic: $ (8.48)us-gaap_EarningsPerShareBasic $ (38.49)us-gaap_EarningsPerShareBasic $ (0.01)us-gaap_EarningsPerShareBasic $ (0.54)us-gaap_EarningsPerShareBasic $ 0.20us-gaap_EarningsPerShareBasic $ 0.68us-gaap_EarningsPerShareBasic $ 0.87us-gaap_EarningsPerShareBasic $ 0.66us-gaap_EarningsPerShareBasic $ (47.52)us-gaap_EarningsPerShareBasic $ 2.40us-gaap_EarningsPerShareBasic $ (6.32)us-gaap_EarningsPerShareBasic
Earnings (loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted:                      
Continuing operations $ (8.48)us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare $ (38.49)us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare $ (0.01)us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare $ (0.54)us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare $ 0.20us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare $ 0.65us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare $ 0.82us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare $ 0.66us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare $ (47.52)us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare $ 2.36us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare $ (6.57)us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare
Discontinued operations $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare     $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare $ 0.01us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare $ 0.01us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare $ 0.25us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare
Earnings (loss) per Common Share Attributable to Cliffs Common Shareholders - Diluted: $ (8.48)us-gaap_EarningsPerShareDiluted $ (38.49)us-gaap_EarningsPerShareDiluted $ (0.01)us-gaap_EarningsPerShareDiluted $ (0.54)us-gaap_EarningsPerShareDiluted $ 0.20us-gaap_EarningsPerShareDiluted $ 0.66us-gaap_EarningsPerShareDiluted $ 0.82us-gaap_EarningsPerShareDiluted $ 0.66us-gaap_EarningsPerShareDiluted $ (47.52)us-gaap_EarningsPerShareDiluted $ 2.37us-gaap_EarningsPerShareDiluted $ (6.32)us-gaap_EarningsPerShareDiluted
Preferred Class A [Member]                      
PREFERRED STOCK DIVIDENDS $ (12.8)us-gaap_DividendsPreferredStock
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassAMember
              $ (51.2)us-gaap_DividendsPreferredStock
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassAMember