Quarterly report pursuant to Section 13 or 15(d)

Commitments And Contingencies (Detail)

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Commitments And Contingencies (Detail) (USD $)
6 Months Ended 24 Months Ended 6 Months Ended 12 Months Ended 6 Months Ended
Jun. 30, 2012
Koolyanobbing Rail Upgrade [Member]
Dec. 31, 2014
Koolyanobbing Rail Upgrade [Member]
Subsequent Event [Member]
Jun. 30, 2012
Bloom Lake [Member]
Dec. 31, 2012
Bloom Lake [Member]
Subsequent Event [Member]
Jun. 30, 2012
Empire And Tilden [Member]
Dec. 31, 2012
Empire And Tilden [Member]
Subsequent Event [Member]
Dec. 31, 2013
Empire And Tilden [Member]
Subsequent Event [Member]
Jun. 30, 2012
Empire [Member]
ton
Jun. 30, 2012
Tilden [Member]
ton
Related Party Transaction [Line Items]                  
Capital investment required     $ 1,300,000,000            
Capital investment committed 33,000,000   819,000,000   203,000,000        
Capital Expenditures related to commitment 17,000,000   369,000,000   169,000,000        
Capital investment, future payments   16,000,000   450,000,000   32,000,000 2,000,000    
Capital investment commitment         $ 245,000,000        
Gross post-project production capacity, metric tons annually               3,000,000  
Increase in production capacity, metric tons annually                 2,000,000