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Property, Plant and Equipment - Additional Information (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Property, Plant and Equipment [Line Items]          
Impairments $ 2,159 $ 2,392 $ 170,079 $ 11,313 $ 15,500
Equity investment impairment loss [1]     3,110    
Western Gas Partners, LP [Member] | Fort Union [Member]          
Property, Plant and Equipment [Line Items]          
Equity investment impairment loss [1]     3,110    
Western Gas Partners, LP [Member] | Granger Complex [Member]          
Property, Plant and Equipment [Line Items]          
Impairments     158,800    
Western Gas Partners, LP [Member] | Granger Complex [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Income Approach Valuation Technique [Member]          
Property, Plant and Equipment [Line Items]          
Estimated fair value 48,500   48,500    
Western Gas Partners, LP [Member] | Equipment [Member]          
Property, Plant and Equipment [Line Items]          
Impairments     11,300   9,400
Western Gas Partners, LP [Member] | Granger Straddle Plant [Member]          
Property, Plant and Equipment [Line Items]          
Impairments     3,700    
Western Gas Partners, LP [Member] | Granger Straddle Plant [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Income Approach Valuation Technique [Member]          
Property, Plant and Equipment [Line Items]          
Estimated salvage value 600   600    
Western Gas Partners, LP [Member] | Northeast Wyoming Facility [Member]          
Property, Plant and Equipment [Line Items]          
Impairments     2,000    
Western Gas Partners, LP [Member] | Northeast Wyoming Facility [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Market Approach Valuation Technique [Member]          
Property, Plant and Equipment [Line Items]          
Estimated salvage value $ 400   $ 400    
Western Gas Partners, LP [Member] | Newcastle System [Member]          
Property, Plant and Equipment [Line Items]          
Impairments         6,100
Western Gas Partners, LP [Member] | Newcastle System [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 Inputs [Member] | Income Approach Valuation Technique [Member]          
Property, Plant and Equipment [Line Items]          
Estimated fair value         $ 3,100
[1] Recorded in Impairments in the consolidated statements of operations.