Quarterly report pursuant to Section 13 or 15(d)

Equity Investments (Investments Accounted for by the Equity Method) (Details)

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Equity Investments (Investments Accounted for by the Equity Method) (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]        
Equity investments and investments in subsidiaries $ 311,694   $ 302,112  
(Income) loss from equity method investments $ (13,536) $ 4,907    
Investment in Tatex Thailand II, LLC        
Schedule of Equity Method Investments [Line Items]        
Approximate ownership % 23.50%      
Equity investments and investments in subsidiaries $ 0   0  
(Income) loss from equity method investments $ (41) (243)    
Investment in Grizzly Oil Sands ULC        
Schedule of Equity Method Investments [Line Items]        
Approximate ownership % 24.9999%      
Equity investments and investments in subsidiaries $ 53,564   57,641  
(Income) loss from equity method investments $ 330 365    
Investment in Timber Wolf Terminals LLC        
Schedule of Equity Method Investments [Line Items]        
Approximate ownership % 50.00%      
Equity investments and investments in subsidiaries $ 980   983  
(Income) loss from equity method investments $ 2 4    
Investment in Windsor Midstream LLC        
Schedule of Equity Method Investments [Line Items]        
Approximate ownership % 22.50%      
Equity investments and investments in subsidiaries $ 30   30  
(Income) loss from equity method investments $ 0 (311)    
Investment in Stingray Cementing LLC        
Schedule of Equity Method Investments [Line Items]        
Approximate ownership % 0.00%      
Equity investments and investments in subsidiaries $ 0      
(Income) loss from equity method investments $ 0 128    
Investment in Blackhawk Midstream LLC        
Schedule of Equity Method Investments [Line Items]        
Approximate ownership % 48.50%      
Equity investments and investments in subsidiaries $ 0   0  
(Income) loss from equity method investments $ 0 0    
Investment in Stingray Energy Services LLC        
Schedule of Equity Method Investments [Line Items]        
Approximate ownership % 0.00%      
Equity investments and investments in subsidiaries $ 0   0  
(Income) loss from equity method investments $ 0 197    
Investment in Sturgeon Acquisitions LLC        
Schedule of Equity Method Investments [Line Items]        
Approximate ownership % 0.00%     25.00%
Equity investments and investments in subsidiaries $ 0   0  
(Income) loss from equity method investments $ 0 68    
Investment in Mammoth Energy Services, Inc.        
Schedule of Equity Method Investments [Line Items]        
Approximate ownership % 25.10%      
Equity investments and investments in subsidiaries $ 179,770   $ 165,715  
(Income) loss from equity method investments $ (13,470) 2,158    
Investment in Strike Force Midstream LLC        
Schedule of Equity Method Investments [Line Items]        
Approximate ownership % 25.00%   25.00%  
Equity investments and investments in subsidiaries $ 77,350   $ 77,743  
(Income) loss from equity method investments $ (357) $ 2,541