Quarterly report pursuant to Section 13 or 15(d)

Fair Value of Financial Instruments (Narrative) (Details)

 v2.3.0.11
Fair Value of Financial Instruments (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
1 Months Ended 3 Months Ended 12 Months Ended 12 Months Ended
Sep. 30, 2009
Jun. 30, 2011
Dec. 31, 2010
Empire [Member]
Jun. 30, 2011
Empire [Member]
Dec. 31, 2002
Empire [Member]
Dec. 31, 2010
U.S. Iron Ore [Member]
Dec. 31, 2013
U.S. Iron Ore [Member]
Jun. 30, 2011
U.S. Iron Ore [Member]
Interest rate on long term receivable 9              
Percent ownership interest     79.00% 79.00% 46.70%      
Long-term receivables     $ 32.8 $ 29.7 $ 120.0 $ 22.3 $ 22.3 $ 22.3
Fair value of the receivable     38.9 35.0   19.5   19.9
Estimated credit-adjusted risk-free interest rate     3.00%     3.80%    
Basis points 350              
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3   $ 20