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Fair Value of Financial Instruments and Concentrations of Credit Risk (Details Textual)
$ in Millions
12 Months Ended
Dec. 31, 2016
USD ($)
customer
Dec. 31, 2015
USD ($)
Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Number of major customers | customer 20    
Receivables, net [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Increase (decrease) in income taxes receivable $ 38.0 $ 29.0  
Nontrade receivables 11.5 10.4  
Environmental services [Member] | Receivables, net [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Escrow deposit $ 8.0 $ 8.0  
Sales revenue, net [Member] | Twenty largest customers [Member] | Customer concentration risk [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Concentration risk, percentage 53.00% 49.00% 40.00%
Sales revenue, net [Member] | Sonatrach [Member] | Customer concentration risk [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Concentration risk, percentage 14.00%    
Accounts receivable [Member] | Sonatrach [Member] | Customer concentration risk [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Concentration risk, percentage 14.00%    
Convertible Notes due 2017 [Member] | Senior notes [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Long-term debt, fair value $ 84.4 $ 154.4  
Convertible Notes due 2021 [Member] | Senior notes [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Long-term debt, fair value   $ 110.5