Annual report pursuant to Section 13 and 15(d)

DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Assets and Liabilities - North American Coal (Details)

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DISCONTINUED OPERATIONS Schedule of Disposal Groups, including Discontinued Operations, Assets and Liabilities - North American Coal (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]      
Discontinued Operation, Tax Effect of Discontinued Operation $ 0 $ 0 $ (6,000,000)
North American Coal [Member]      
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]      
Loss Contingency Accrual 0 2,100,000  
Disposal Group, Including Discontinued Operation, Accrued Liabilities 0 1,100,000  
Disposal Group, Including Discontinued Operation, Other Liabilities, Current 3,200,000 4,900,000  
Disposal Group, Including Discontinued Operation, Liabilities 3,200,000 6,000,000  
Discontinued Operation, Tax Effect of Discontinued Operation 0 0 200,000
Canadian Entities [Member]      
Schedule of Disposal Groups, Including Discontinued Operations, Assets and Liabilities [Line Items]      
Cost Method Investments 0 0  
Discontinued Operation, Tax Effect of Discontinued Operation $ 0 $ 0 $ 5,800,000